I am once again, asking for your help

So idk what the best way to go about deep cleaning my SN files, I want to go through and get rid of all the stuff I don’t need/ use anymore, but I want to keep some of it (cars, trucks, guns, some BGs and effects among other little odds and ends)

What would be the best way to purge? Go through and do it all by hand or save all the important files somewhere external and just delete and reinstall SN?