A dumb question from my side...
Is this body an unparametric body? If yes then it will not be a straight forward process (Delete face as suggested by @GaneshKadole and other manual work will be required...you can infact delete the blend faces quite effectively using proper selection filters).
If the model is a complete parametric one then you can go up in your feature history make the main primitive body (without any pocket/blends etc.) a current feature and use Extract Body.
I tried delete face but gives error as there are curves on the part. I think delete face is not useful. I tried covering the body with extrude than subtract it but nothing came up
It would be easy to help you if you can upload that particular part file here.