Formula milk for preemie

Dear Preemie Momshies, my preemie was born 32 weeks 1.57 kg., current age 1 month 21 days. Cw is 3 kgs. Accdg to his dr puede n magswitch from similac neosure to regular milk brand. Ano po milk ng preemie nyo na maganda for weight gain and brain development? Pa-share naman po pls.... Many thanks in advance!!!