Both STL (3D printing format) and A3D (Amapi 3D modeling files) files contain 3D/CAD data, so with a proper CAD converter or CAD software you can easily transform .stl files and save them as .a3d files. Not all aspects of the drawings/models/parts might be translated however, nevertheless stl to a3d conversion usually works well with meshes.
Updated: September 30, 2022