I have a .stl file of a volar locking plate. To work on plate positioning I need to find the locations of the screw holes in this plate.

I have tried projecting the mesh points onto the xy plane, to see where the holes are. But only projecting the points does not show the holes as there are regions in stl files with low density of points (flat surfaces)

How do I find the coördinates of the holes in my STL file? they are not all cylindrical