Can someone please Help me with this?

I'm Making a Gui that inserts a Part onClicked the Part Inserts but the size doesn't change Can Some One Please Help?

function onMouseButton1Click()
	p = Instance.new("Part", game.Workspace)
	p.Anchored = true
	p.Size = UDIM2.new(12.04, 9.69, 2)
end
script.Parent.MouseButton1Click:connect(onMouseButton1Click)

Parts use Vector3, GUIs use UDim2

function Click()
	local Part=Instance.new("Part",workspace)
	Part.Anchored=true
	Part.FormFactor="Custom"
	Part.Size=Vector3.new(12.04,9.69,2)
end