How to get my 3 week old to sleep longer than 3 hours at night

Bailey

My 3 week old is an incredible sleeper - she sleeps all day and usually 3/3.5 hours each time, but I can’t seem to get that time to extend at night. She was preemie (5 weeks early) so not sure if that has anything to do with it. But any tips/tricks would be greatly appreciated!