Some 3D modeling programs can process .stl files used in 3D printing and recover the data back to the original 3D model or part file (.prt). For example SolidWorks has this function, but you may probably find other programs capable of this conversion.
Convert Stereolithography CAD file to CAD 3D part or component.
We have found 2 software records in our database eligible for .stl to .prt file format conversion.
Microsoft Windows software - convert stl to prt on Windows
A 2D and 3D CAD construction software
Convert from stl file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned stl to prt. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Set of 3D CAD/CAM/CAE design tools from PTC