My general rule during whelping
, is that I want to have a puppy out within 1-2 hours of contractions. There can be breaks between puppies that can last 2-4 hours, but once contractions start back up again, they should have the puppy out fairly quickly.
If the last puppy was 2 hours ago and she's still contracting, then it's been too long. In that case, I would opt for a c-section to get the puppies out. I also prefer a c-section when we have multiple dead puppies. Dead puppies do not secrete Cortisol. It is the puppy secreting cortisol that stimulates the uterus to continue contracting.
The chance of live puppies after 2 dead goes down significantly. Dead puppies in the uterus will contain bacteria and they are at increased risk of early placental separation. The safest and best option here is to get to a vet and do a c-section.
As to how many more are in there, it's just a guess right now. It could be none, it could be 1, it could be 5+. Without x-rays, we just don't know.
I hope this helps, let me know if you have any other questions.