Dear Eldho Paul, I think you meant "surfase model" instead of "shell model", there is a tutorial how to make a surfase model from a solid model. It is called:

Solidworks advanced tutorial | How to convert solid to surface model? - YouTube

And you can always give thickness again to the surfase model if you want

Thanks, Dmitrii for the reply. I need a hollow model of this with 12 mm thickness. I tried in solid works but its difficult to convert a (.step file) into a hollow model of 12mm thickness.