STL MESH MODEL TO SMOOTH SOLID BODY - BIG DADDY FROM BIOSHOCK GAME

I have an STL of the character "BIG DADDY" from the BIOSHOCK games. I need it to convert to a smooth solid body using Inventor, Rhino 3D, Fusion 360 or similar. I have already redraw some parts using SPACECLAIM but there are some surfaces that are a bit complex and I can't do it properly.