the stl format insert it as facet feature if you have the rex module.
is a triangular data file used for stereolithography (fast protection) and reverse engineering.
you cannot transform it into parasolid, it does not contain solid surfaces or entities.
It is usually seen by solidworks as a graphic entity.
Is it a complex piece?
If it's not too complex, I can help you.
on the stl you have to model the part and then carry it in parasolid.
Can you post the file?
If you can't, send me your references in private.