Can someone help me with this welding error?

local enabled = true
Player = script.Parent.Parent
mouse = Player:GetMouse()
run = game:GetService("RunService")
local Left_Arm = script.Parent:FindFirstChild("Left Arm")
local Right_Arm = script.Parent:FindFirstChild("Right Arm")
local Core = script.Parent:FindFirstChild("Torso")
local Left_Leg = script.Parent:FindFirstChild("Left Leg")
local Right_Leg = script.Parent:FindFirstChild("Right Leg")
function onKeyDown(key)
    key = key:lower()
    if key == "t" then
        game:GetService("Chat"):Chat(Player.Character.Head, "Focus the mind, reflect upon yourself, and determine the goal.")
        Left_Arm = Instance.new ("Part")
        Right_Arm = Instance.new("Part")
        Core = Instance.new("Part")
        Left_Leg = Instance.new("Part")
        Right_Leg = Instance.new("Part")
        Left_Arm.BrickColor = BrickColor.new("White")
        Left_Arm.Size = Vector3.new(2, 3, 2)
        Left_Arm.TopSurface = "Smooth"
        Left_Arm.BottomSurface = "Smooth"
        Left_Arm.Transparency = 0.7
        Left_Arm.CanCollide = false
        Left_Arm.CFrame = Player.Character["Left Arm"].CFrame *CFrame.new(2, 3, 2)
        Left_Arm.Parent = workspace
        Right_Arm.BrickColor = BrickColor.new("White")
        Right_Arm.Size = Vector3.new(2, 3, 2)
        Right_Arm.TopSurface = "Smooth"
        Right_Arm.BottomSurface = "Smooth"
        Right_Arm.Transparency = 0.7
        Right_Arm.CanCollide = false
        Right_Arm.CFrame = Player.Character["Right Arm"].CFrame *CFrame.new(2, 3, 2)
        Right_Arm.Parent = workspace
        Core.BrickColor = BrickColor.new("White")
        Core.Size = Vector3.new(3, 3, 2)
        Core.TopSurface = "Smooth"
        Core.BottomSurface = "Smooth"
        Core.Transparency = 0.7
        Core.CanCollide = false
        Core.CFrame = Player.Character["Torso"].CFrame *CFrame.new(3, 3, 2)
        Core.Parent = workspace
        Left_Leg.BrickColor = BrickColor.new ("White")
        Left_Leg.Size = Vector3.new(2, 3, 2)
        Left_Leg.TopSurface = "Smooth"
        Left_Leg.BottomSurface = "Smooth"
        Left_Leg.Transparency = 0.7
        Left_Leg.CanCollide = false
        Left_Leg.CFrame = Player.Character["Left Leg"].CFrame *CFrame.new(2, 3, 2)
        Left_Leg.Parent = workspace
        Right_Leg.BrickColor = BrickColor.new("White")
        Right_Leg.Size = Vector3.new(2, 3, 2)
        Right_Leg.TopSurface = "Smooth"
        Right_Leg.BottomSurface = "Smooth"
        Right_Leg.Transparency = 0.7
        Right_Leg.CanCollide = false
        Right_Leg.CFrame = Player.Character["Right Leg"].CFrame *CFrame.new(2, 3, 2)
        Right_Leg.Parent = workspace
        local weld = Instance.new("Weld")
        weld.part0 = Left_Arm
        weld.C0 = Left_Arm.CFrame:inverse()
        weld.part1 = script.Parent:FindFirstChild("Left Arm")
        local weld2 = Instance.new("Weld")
        weld2.part3 = Right_Arm
        weld2.C3 = Right_Arm.CFrame:inverse()       
    end
end

mouse.KeyDown:connect(onKeyDown)

My blocks don't stick to my arms,legs,and torso and i get this error. 09:01:58.553 - part0 is not a valid member of Weld