Dear, there should be no concept of fromula milk for new born babies until your milk supply is sufficient. For new born babies feed in every 2 hours interval for atleast 10-15 min .. if baby is sleeping then 4 hours interval is fine. Don't force feed until 4 hours gap. And you can dream feed the bbay is baby is allowing you. And please avoid formula milk. Breastmilk is sufficient for your baby.