Newborn puppies need mother's milk. Dogs milk has the correct balance of nutrients to support growth and development of the newborn pup. Also, it is particularly important the newborn puppies nurse within 24 hours of birth. The milk that the mother produces during this critical period is called colostrum. Colostrum is high in maternal antibodies which are important for the immune system of the pup in the first few weeks of life. During the first 24 hours the pups are able to absorb these antibodies through the intestinal wall. Pups will rely on the mother as their complete food source until abe 3-4 weeks. At this time, the owner should introduce a solid food soaked in water. This is to allow the pups to grow accustomed to the feel, smell and taste of solid food. Weaning will occur naturally until at 8-12 weeks the pups will be eating solids only.
If you have orphaned newborn pups to care from, you should seek veterinary advice as to hand rearing them. They will require milk-replacer which is available from your vet, and you may be able to borrow other equipment from the vet to better feed them. You will also have to mimic the action of the mother cleaning her pups in order to stimulate them to urinate and defaecate. This can be done by using a towel moistened with warm water to clean their perianal area. The other vital requirement is warmth. Hand rearing is a lot of work and requires patience and commitment. Again, I would recommend getting some advice from your vet.