Wheels is not a valid member of Model?

When I run the script, I get an error where it says that: Wheels is not a valid member of Model

so i was making a car but got a error of the wheels not being a valid member of model

Script:

local JS = game:GetService("JointsService")
function MakeWeld(x,y,type,s) 
    if type==nil then type="Weld" end
    local W=Instance.new(type,JS) 
    W.Part0=x W.Part1=y 
    W.C0=x.CFrame:inverse()*x.CFrame 
    W.C1=y.CFrame:inverse()*x.CFrame 
    if type=="Motor" and s~=nil then 
        W.MaxVelocity=s 
    end 
    return W    
end

function ModelWeld(a,b) 
    if a:IsA("BasePart") then 
        MakeWeld(b,a,"Weld") 
    elseif a:IsA("Model") then 
        for i,v in pairs(a:GetChildren()) do 
            ModelWeld(v,b) 
        end 
    end 
end

function UnAnchor(a) 
    if a:IsA("BasePart") then a.Anchored=false  end for i,v in pairs(a:GetChildren()) do UnAnchor(v) end 
end
--
script.Parent:WaitForChild("A-Chassis Interface")
script.Parent:WaitForChild("Plugins")
script.Parent:WaitForChild("README")

local car=script.Parent.Parent
local _Tune=require(script.Parent)

local Drive=car.Wheels:GetChildren()

function getParts(model,t,a)
    for i,v in pairs(model:GetChildren()) do
        if v:IsA("BasePart") then table.insert(t,{v,a.CFrame:toObjectSpace(v.CFrame)})
        elseif v:IsA("Model") then getParts(v,t,a)
        end
    end
end

for _,v in pairs(Drive) do

    for _,a in pairs({"Top","Bottom","Left","Right","Front","Back"}) do
        v[a.."Surface"]=Enum.SurfaceType.SmoothNoOutlines
    end

    local WParts = {}

    local tPos = v.Position-car.DriveSeat.Position
    if v.Name=="FL" or v.Name=="RL" then
        v.CFrame = car.DriveSeat.CFrame*CFrame.Angles(math.rad(90),0,math.rad(90))
    else
        v.CFrame = car.DriveSeat.CFrame*CFrame.Angles(math.rad(90),0,math.rad(-90))
    end
    v.CFrame = v.CFrame+tPos

    if v:FindFirstChild("Parts")~=nil then
        getParts(v.Parts,WParts,v)
    end
    if v:FindFirstChild("Fixed")~=nil then
        getParts(v.Fixed,WParts,v)
    end

    if v.Name=="FL" or v.Name=="FR" then
        v.CFrame = v.CFrame*CFrame.Angles(math.rad(_Tune.FCamber),0,0)
        if v.Name=="FL" then
            v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(_Tune.FToe))
        else
            v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(-_Tune.FToe))
        end
    elseif v.Name=="RL" or v.Name=="RR" then
        v.CFrame = v.CFrame*CFrame.Angles(math.rad(_Tune.RCamber),0,0)
        if v.Name=="RL" then
            v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(_Tune.RToe))
        else
            v.CFrame = v.CFrame*CFrame.Angles(0,0,math.rad(-_Tune.RToe))
        end
    end

    for _,a in pairs(WParts) do
        a[1].CFrame=v.CFrame:toWorldSpace(a[2])
    end

    if v.Name=="FL" then
        v.CFrame = v.CFrame*CFrame.Angles(0,math.rad(-_Tune.FCaster),0)
    elseif v.Name=="FR" or v.Name=="F" then
        v.CFrame = v.CFrame*CFrame.Angles(0,math.rad(_Tune.FCaster),0)
    elseif v.Name=="RL" then
        v.CFrame = v.CFrame*CFrame.Angles(0,math.rad(-_Tune.RCaster),0)
    elseif v.Name=="RR" or v.Name=="R" then
        v.CFrame = v.CFrame*CFrame.Angles(0,math.rad(_Tune.RCaster),0)
    end

    local arm=Instance.new("Part",v)
    arm.Name="Arm"
    arm.Anchored=true
    arm.CanCollide=false
    arm.FormFactor=Enum.FormFactor.Custom
    arm.Size=Vector3.new(1,1,1)
    arm.CFrame=(v.CFrame*CFrame.new(0,_Tune.StAxisOffset,0))*CFrame.Angles(-math.pi/2,-math.pi/2,0)
    arm.TopSurface=Enum.SurfaceType.Smooth
    arm.BottomSurface=Enum.SurfaceType.Smooth
    arm.Transparency=1

    local base=arm:Clone()
    base.Parent=v
    base.Name="Base"
    base.CFrame=base.CFrame*CFrame.new(0,1,0)
    base.BottomSurface=Enum.SurfaceType.Hinge

    local axle=arm:Clone()
    axle.Parent=v
    axle.Name="Axle"
    axle.CFrame=CFrame.new(v.Position-((v.CFrame*CFrame.Angles(math.pi/2,0,0)).lookVector*((v.Size.x/2)+(axle.Size.x/2))),v.Position)*CFrame.Angles(0,math.pi,0)
    axle.BackSurface=Enum.SurfaceType.Hinge

    if v.Name=="F" or v.Name=="R" then
        local axle2=arm:Clone()
        axle2.Parent=v
        axle2.Name="Axle"
        axle2.CFrame=CFrame.new(v.Position+((v.CFrame*CFrame.Angles(math.pi/2,0,0)).lookVector*((v.Size.x/2)+(axle2.Size.x/2))),v.Position)*CFrame.Angles(0,math.pi,0)
        axle2.BackSurface=Enum.SurfaceType.Hinge
        MakeWeld(arm,axle2)
    end

    MakeWeld(car.DriveSeat,base)
    if v.Parent.Name == "RL" or v.Parent.Name == "RR" or v.Name=="R" then
        MakeWeld(car.DriveSeat,arm)
    end

    MakeWeld(arm,axle)

    arm:MakeJoints()
    axle:MakeJoints()


    if v:FindFirstChild("Fixed")~=nil then
        ModelWeld(v.Fixed,axle)
    end

    if v:FindFirstChild("Parts")~=nil then
        ModelWeld(v.Parts,v)
    end

    if v:FindFirstChild("Steer") then
        v:FindFirstChild("Steer"):Destroy()
    end

    local gyro=Instance.new("BodyGyro",v)
    gyro.Name="Stabilizer"
    if v.Name=="FL" or v.Name=="FR"  or v.Name=="F" then
        gyro.D=_Tune.FGyroD
        gyro.MaxTorque=_Tune.FGyroMaxTorque
        gyro.P=_Tune.FGyroP
    else
        gyro.D=_Tune.RGyroD
        gyro.MaxTorque=_Tune.RGyroMaxTorque
        gyro.P=_Tune.RGyroP
    end

    if v.Name=="FL" or v.Name=="FR" or v.Name=="F" then
        local steer=Instance.new("BodyGyro",arm)
        steer.Name="Steer"
        steer.P=_Tune.SteerP
        steer.D=_Tune.SteerD
        steer.MaxTorque=Vector3.new(0,_Tune.SteerMaxTorque,0)
        steer.cframe=base.CFrame
    else
        MakeWeld(base,axle,"Weld")
    end

    local AV=Instance.new("BodyAngularVelocity",v)
    AV.Name="#AV"
    AV.angularvelocity=Vector3.new(0,0,0)
    AV.maxTorque=Vector3.new(_Tune.PBrakeForce,0,_Tune.PBrakeForce)
    AV.P=1e9
end

for i,v in pairs(script:GetChildren()) do
    if v:IsA("ModuleScript") then
        require(v)
    end
end

wait()
ModelWeld(car.Body,car.DriveSeat)

local flipG = Instance.new("BodyGyro",car.DriveSeat)
flipG.Name = "Flip"
flipG.D = 0
flipG.MaxTorque = Vector3.new(0,0,0)
flipG.P = 0

wait()

UnAnchor(car)

script.Parent["A-Chassis Interface"].Car.Value=car
for i,v in pairs(script.Parent.Plugins:GetChildren()) do
    for _,a in pairs(v:GetChildren()) do
        if a:IsA("RemoteEvent") or a:IsA("RemoteFunction") then 
            a.Parent=car
            for _,b in pairs(a:GetChildren()) do
                if b:IsA("Script") then b.Disabled=false end
            end 
        end
    end
    v.Parent = script.Parent["A-Chassis Interface"]
end
script.Parent.Plugins:Destroy()

car.DriveSeat.ChildAdded:connect(function(child)
    if child.Name=="SeatWeld" and child:IsA("Weld") and game.Players:GetPlayerFromCharacter(child.Part1.Parent)~=nil then
        local p=game.Players:GetPlayerFromCharacter(child.Part1.Parent)
        car.DriveSeat:SetNetworkOwner(p)
        local g=script.Parent["A-Chassis Interface"]:Clone()
        g.Parent=p.PlayerGui
    end
end)
car.DriveSeat.ChildRemoved:connect(function(child)
    if child.Name=="SeatWeld" and child:IsA("Weld") then
        for i,v in pairs(car.DriveSeat:GetChildren()) do
            if v:IsA("Sound") then v:Stop() end
        end
        if car.DriveSeat:FindFirstChild("Flip")~=nil then
            car.DriveSeat.Flip.MaxTorque = Vector3.new()
        end
        for i,v in pairs(car.Wheels:GetChildren()) do
            if v:FindFirstChild("#AV")~=nil then
                if v["#AV"].AngularVelocity.Magnitude>0 then
                    v["#AV"].AngularVelocity = Vector3.new()
                    v["#AV"].MaxTorque = Vector3.new()
                end
            end
        end
    end
end)