Conversion from CATPart to SLDPRT is not supported yet :(

CATPart is a native format developed by Dassault Systems for storing parts of the assemblies created in CATIA V5 software suite, which is extensively used in mechanical engineering including aerospace, automotive, shipbuilding and other domains.

CATPart stores geometry, structure and metadata of 3D models dedicated to single parts. Multiple CATPART files can be combined into a CATProduct assembly file.

Among CAD applications that support CATPart extension are Autodesk Inventor, Fusion 360, and 3ds Max.

A SLDPRT file contains a 3D part created in the SOLIDWORKS design software.

Multiple SLDPRT parts can be independently modified and combined into a single SLDASM assembly file. If one SLDPRT part belongs to several assemblies, then after modifying it, the changes will appear in all assemblies.

SLDPRT are proprietary files with closed specifications. Nevertheless, some APIs (like CAD Exchanger SDK) provide the facility to read and convert them to other formats.

In addition to SOLIDWORKS software, SLDPRT files are supported by Autodesk Fusion 360.