How many babies do starfish have?

Your question contains a misunderstanding. Starfish are not mammals, and therefore do not give birth to live young like humans or other animals referred to as "mammals." Starfish belong to the phylum Echinodermata, and they reproduce sexually by releasing sperm and eggs into the water, where fertilization takes place. Each adult starfish can produce a significant number of eggs and sperm during their breeding season, but the exact number can vary widely among species.