I've tried everything but my part wont copy?

local Donkey = script.Parent

while true do wait(6.1) Donkey:Destroy()

wait(8)
local comeback = Donkey:Clone()
comeback.parent = game.Workspace
comeback.postion = Vector3.new(352, 9, -61)

end

Well, you destroyed the Donkey before you cloned it.

while true do wait(6.1) 

Donkey:Destroy()

wait(8)

local comeback = Donkey:Clone()

You can't clone something that doesn't exist.

It's because of exactly what the first comment said; Destroying an object will lock its parent to nil. Also, the spelling isn't correct. The error was most likely parent is not a valid member of Part because the property is Parent, not parent. What the script should be is this:

local Donkey = script.Parent

while true do wait(6.1)
	Donkey.Parent = nil
	wait(8)
	Donkey.Parent = workspace
	Donkey.Position = Vector3.new(352, 9, -61)
end