Hi there, new to cad, and 3d in general

I am working on a project that I am having cut out on a cnc machine and need help.

I have drawn a 3d model of a box in 5 separate peices with correct measurments etc in software online called tinkercad. Really easy to use quick and dirty 3d drawing software and the company that is going to cut it out for me needs a dxf, step, or parasolid drawing in order to cut the plastic out.  tinkercad only lets me export to .stl or .obj, neither of which they can use.  is there anyone here that can help me?