how to link bodys to difrent files?

In SolidWorks these are referred to as external references. If you have multiple bodies in a single part, go into the "solid bodies" folder. Right click on one of the bodies and choose insert into new part. This will give you a part without a feature history, but by default this will refer back to the original part. When you modify the body in the original part, the file with the single body will update.

  1. Step 1:

    Insert into new part

  2. Step 2:

    new part