Part not moving?

So, I literally just want this model's children to move when a part is clicked, however I get this message: "bad argument #1 to '?' (Vector3 expected, got nil)" which I've never come across before. Any help to fixing this will be appreciated.

x = script.Parent:GetChildren()
script.Parent.ClickDetector.MouseClick:connect(function()
x.Position = x.Position + Vector3.new(5,5,5)
end)