SolidWorks supports import of files saved in STEP product data files (.stp, .step) and can use them for making new Solidworks technical files, which include assemblies (.sldasm). Such step to sldasm conversion might also be possibly achieved by using a CAD translation software or through some 3rd party CAD/3D modeling software.
Open STEP file Open SLDASM fileA CAD visualizaton, analyzation and translating system