How can I convert a vector3 into a Udim2 in a localscript?
Do you mean a Vector2? A Vector3 has 3 components while a UDim2 has 2x2 components, so one of them will go unfinished.
local vec = Vector2.new(1, 2) -- 1, 2
UDim2.fromScale(vec.X, vec.Y) --> 1, 0, 2, 0
UDim2.fromOffset(vec.X, vec.Y) --> 0, 1, 0, 2