Depends on the shape.
One possible method would use the Intersection Curves tool with reference planes or surfaces.
What do you mean by "extract"? Do you mean take measurements? You can use the Measure tool for that.
If you looking for extracting the shape of the body, use offset surface tool.
Perform the offset surface at 0 mm, you would be able to convert the outer shape of the body.
Thanks & Regards,