How to extract XYZ coordinates from a curve or surface?

Hi! I've got a curved surface with some surface roughness(shown below) and I'm going to get this surface flattened with the same surface roughness and get this flat surface 3D printed. So I need information about these surface roughness(e.g the height of the roughness etc). How can I extract the coordinates of the points on this surface or a single curve on the surface? Do I need to draw points on the surface manually?
Or is there an easier way to get the information about the surface roughness?
Many thanks in advance!