I'm a student and need to know if a man finds out his the father of a child that has been put up for adoption what are his rights

He needs to step forward and announce that he is the father to obtain any rights. If the mother denies that he is the father a paternity tests may be needed. You may be better served to consult a lawyer since this may get messy, mom knew who the father was and still offered the child to adoption so what's she thinking.