Dennis
I use Rhino6. Your software experience may help with those other advanced 3D modeling programs. But you might want to start out with less intensive programs. Even today I use less than 5% of Rhino.
Anyway you get to .stl or .obj model formats will work.
You may want to take a look a the Formlabs website too. A lot of universal tech on placing and orienting models so they print well.