first install freecad and open the stl in freecad to turn it into an solid and export in .step, and then open .step file in solidworks and you are done.
Short tutorial on how to edit an STL mesh using FreeCAD.
Edit 3D CAD stl file from SOLIDWORKS to solid for ROS Fanuc link. This link can be visualised in rviz.The draft master can be followed in more detail in .
