Convert 3DS or OBJ mesh file to Solid Part (IGES or SLDPRT)

I need to convert 2 files, one pharoah mask and one anubis (doglike) figure) from surface files to solid parts attached to a rectangular base file I have already made. I have both files in 3DS and OBJ and need a completely solid model saved preferably as a PRT or SLDPRT file but I will accept an IGS file. I have attached pdfs showing the parts rendered as they should approximately look after conversion.