How to Select Unit Movement in a RTS style?

Goal: I would like to select a player created troop and move the troop to the mouse.Target smoothly.

This is what I have currently:

Local Script - Highlights the first selected part [1] of the array and sends the first part over to the server, this is what I want sent.

local function HightlightPart(part)
    local box = table.remove(Boxes.Cache, 1)

    if not box then
        box = Instance.new("SelectionBox")
        box.LineThickness = 0.05
        box.Adornee = part
        box.Parent = workspace
    end
    box.Adornee = part

    table.insert(Boxes.InUse, box)
end
local function UnhightlightPart(part)
    local position, box
    for i,selection in pairs(Boxes.InUse) do
        if selection.Adornee == part then
            position = i
            box = selection
        end
    end

    if box then
        box.Adornee = nil
        table.insert(Boxes.Cache, table.remove(Boxes.InUse, position))
    end
end

mouse.Button1Down:Connect(function()

    local SelectMultiple = UserInputService:IsKeyDown(Enum.KeyCode.LeftShift)
    local Target = mouse.Target
    local MousePos = mouse.Hit.p

    local check = table.find(Selected, Target)
    if Target and Target.Parent then
        if Selected then
            MousePosServerTransfer:FireServer(Selected[1], MousePos)
            UnhightlightPart(part)
            table.remove(Selected, check)
        end

        if SelectMultiple then
            if check then
                UnhightlightPart(Target)
                table.remove(Selected, check)
            else
                HightlightPart(Target)
                table.insert(Selected, Target)
            end
            elseif not check then
                HightlightPart(Target)
                table.insert(Selected, Target)
            end
    elseif not SelectMultiple then
        for _,part in pairs(Selected) do
            UnhightlightPart(part)
        end
        table.clear(Selected)
    end
end)

Server Script - Makes the part move to the mouse position of the client.

RP:WaitForChild("Client"):WaitForChild("Remotes"):WaitForChild("UnitMove").OnServerEvent:Connect(function(plr, part, MousePos)
    print("Recieved:", MousePos)
    part.Position = MousePos
    part.CFrame = CFrame.new(MousePos)
end)

All the variables are sorted out. Please comment if you want me to elaborate, sorry if it is messy.

This is the best version I can produce but if anyone can improve the script or give me an explanation, please help, thanks.