I have a couple old Labs and one has fatty tumors. You can google this and find out info, but from what I know ( and you should really take him to a Vet), if you can move them around, they don't interfere with organs, they are not on feet, or face- like eyelids, that would cause them a problem, then you may be looking at a benign tumor.
But your dog has a tumor near his scrotum and, I would worry about this. Take him to a vets to be sure.
This sounds a lot like a Lipoma (benign tumor of fatty tissue) The only way to know exactly what it is and whether it needs to come off, is take him to the vet and get it needle-biopsied.