You need to separate the hen and her babies from the rest of the flock. Put her and the babies in a large dog crate with plenty of clean shavings, chick food (mama doesn’t need layer feed, chick food is fine) and fresh water that is in a container the chicks can reach but won’t drown in. All you need to do is provide shelter, food and water. Mama will keep them warm underneath her. I would suggest putting them in a a shed or garage. In a week or so, you should move them all outside together but still separated from the rest so your big chickens don’t pick on the little ones and eat all the chick food. Mama will do all the rest.
