A general guideline to feeding a complete, balanced raw diet is %80 muscle meat, %10 bone and %10 organs and out of that %5 should be liver and %5 other organs. But this is just a starting point, some dogs maybe need less or more bone in the diet, for example. You also start by feeding %2-%3 of the ideal body weight of the dog. Puppies need a little more at first obviously, so depending on your pups age I would maybe do closer to %5 or %6 of his weight and go from there...that would be for a 3 - 5 month old puppy, at about 6 months you gradually start to decrease the amount of food.
I thought I saw that the Primal grinds had bone, meat and organs? You would have to look further into it I'm not sure. Check out what varieties and ingredients they have. If you can find another premade that offers a balanced diet then give it a shot, it also does not hurt to use a few different brands.
If your pup is currently 8 lbs, and depending on his age I would start with 0.45 - 0.50 lbs (about 7 - 8 ounces) of food per day, broken into two meals daily, and adjust accordingly if your pup is getting too fat or too thin. For a general guideline, going by a %6 feeding ratio (which is recommended for puppies on the raw food calculator I use), which is 0.48 lbs, out of this the 80/10/10 ratio would be 0.384 lbs meat, 0.048 bone, and 0.048 organs. Most people like to balance over a week rather than figure it out daily as it can be a lot of work, and most commercial raw foods are balanced anyway, but if your going to add in some extra's you just want to ensure you include it into the balance so your not throwing it off.
I think though, sticking to ground/premade is the best route to go for young puppies who's teeth haven't quite yet fully developed..unless you are able/willing to ground up and prepare your own raw food - this way you don't have to worry about them choking because they can't chew up bones properly. My dogs both ate a fully balanced commercial ground raw from about 3 months to 6 months old. I dont know but that's probably what I would do until he's older and his teeth and jaw are fully developed, once he's matured more you can start adding in some PMR and raw meaty meals if you wish..
You can start out a PMR diet by feeding stuff like chicken/turkey or duck necks, chicken quarters, chicken backs, chicken wings etc. From there you can gradually add in other proteins like beef, pork, fish and other red meats and some organs like beef/chicken liver, heart, gizzards etc or whatever else is easily available to you. Things like raw eggs, tripe, etc are good to supplement occasionally, and if you are unable to get oily raw fish, fish oil is a common supplement amongts some raw feeders as well..My Shiba really likes fish, and he does extremely well on it. I feed him whole raw frozen sardines I get from the frozen meat section at my grocery store and he gets at least one per week, I usually cut it up and serve mixed in with other meals.
I still feed some commercial raw, its %100 balanced though and contains only meat, bone and organs - no extras, and the brands I feed use mainly grass fed animals or free range. I feed them this when its convenient like busy weekday mornings. Aside from that they get prey model and I try to balance accordingly, surely I'm not always accurate but its balance over time and I go by my dogs, and signs they're bodies tell me if they need a little more of this or that, and I use as many different proteins as possible and offer as many as I can in a day. Usually they get 1 or 2 different proteins for breakfast, then 1 or 2 entirely different ones for dinner. This is another reason I like having commercial raw on hand, between the 3 or 4 different brands I buy, and between all the prey model I have, I'm able to offer about 12 different animal proteins on a weekly basis.
Hopefully you can find a good, balanced commercial/premade raw to start out with, and like I mentioned previously chicken is the best to start out with.. then slowly and gradually you introduce new proteins from there. Since your pup is still young, the transition period on to raw shouldn't be too bad for him, usually most people say that the longer a dog has been eating kibble, the longer the transition period is. I don't really know myself since both of my dogs have been raw fed since puppies, and have never had any issues.
Good luck, and we would love to see some pics of your puppy