How much to feed 6 weeks old?

My baby is 3 weeks old and she drinks FM 110ml pee feed every 3hours. I think each baby is different so there is no exact volume and how much they shd drink? I was initially also confused if bb drink too much or too little but PD says just give, trial and error as long as bb not rejecting the volume means it is ok

Yes that's fine unless you do BF direct latch then that's like 20 to 45 mins depending on baby's milk intake. For FM that's fine with interval of 3 hrs gap.