I was about to suggest that… 
Below is the relevant script from the collection - exports selected objects one per file with a numbering scheme. Comes with 4 preset mesh densities. It can be adjusted to taste (different naming/numbering settings, different .stl settings) if you need… The default export location if the file has been saved is the current 3dm file’s folder. Should run on Mac or Win --Mitch
BatchExportSTLByObjWSett.py (3.7 KB)