Are you asking if you should register with "NAPR?"
I just looked them up (never heard of them) and they say they register purebred dogs.
But how do they determine this? Based on the questions they ask (breeders name, sire and dams name) it looks like they're just googling the info. to see if your dog (or his family tree) is AKC registered. If so, you're in.
If that's the case, they should be ashamed of themselves.
In essence, you're providing the info. (registered your dog with AKC, and the breeders registered the sire and dam with AKC too) and paying NAPR for the info. you already provided AKC. It's a bulls**t registry.
But I could be wrong (I'm very pessimistic lately.) So I'd send them an email asking how they prove the dogs registered with them are purebreds.