Best formula milk for constipation newborn

My baby will be 1 month soon. Been giving her formula milk lactogen 1 and I realise for the past few weeks she is having constipation. Will only poop after 4 days. or some days she will poop like very small hard stool. But so far no vomiting or rash. Want to try to change the formula milk. Any recommendations on what formula milk is good for constipation newborn?