I'm not sure exactly what you mean but here are two way's to get "a part's surface gui position".
Detecting the side of a SurfaceGui
It's pretty simple to do this, all you need is a variable and the SurfaceGui object.
side = game.Workspace.Part.SurfaceGui.Face
print("The side of the SurfaceGui is".. side)
Detecting the position of a SurfaceGui
position = game.Workspace.Part.SurfaceGui.AbsolutePosition
print("The position of the SurfaceGui is".. position)
Hopefully I understood your question and helped.
If this helped, please go ahead and accept this answer.
3 comments
Depends on what part of the Surface GUI you are looking for. Example: The frames and components involved inside the surfaceGUI
Which reference frame, the camera's or looking straight at the GUI?
You need to rephrase your question, im pretty sure we are all confused