Since both the SLDPRT and CAD are file formats of same purpose (CAD drawings / data), it should be quite possible to perform conversion between each other. CAD file type was usually mainly in the past, yet some programs like BobCAM-CAM Mill still support it (or at least one of them).
Convert SolidWorks CAD part to CAD drawing file.
We found one software available in the database for this conversion.
Microsoft Windows software - convert sldprt to cad on Windows
A CAD-CAM software for CNC Milling
Convert from sldprt file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.