part to stp conversion in general sense represents export of any 3D CAD part to ISO STEP format, something that is certainly doable. The best known .part files do come from PTC Pro/Engineer or it's successor Creo, so these are most likely what users looking for this export needed. But numerous other tools use .prt or .part files to store 3D CAD part content, so there can always be alternative conversions as well. In any case, you will need tool that supports your particular type of .part files.
Updated: July 28, 2023