to convert polygons to subdiviions you must first have a good modeled surface or object. which means all of its faces should be in quads. then simply modify > convert > poly to subdivision > the max base mesh faces should be a high enough number to turn your polygon into a subdi, and the maximum edges per vetex should be set high enough so that it can make enough vertex to support your model.
9 months into Maya...and still learning...
0 experience with any other 3D programs