Milk intake

My baby is 1 mth old. He is currently on milk formula and feeding at 90ml each feed. He drinks every 2.5 hourly, about 10 feeds each day. How would I know if he is feeding enough or underfeed? When do I increase his milk intake? I was also thinking abt increasing the milk intake for the feed at night so he can sleep longer. But I am not sure if I will be giving him too much