help!

liv • KANSAS🌾HAPPY✌🏼️
I have twin girls, they are 5 going on 6 weeks old. They sleep 3-4 hours in between feedings during the day and at night they are up every hour and a half or 2 hours! Any tips on how I can switch that?! They have their nights and days mixed up. Also when did your little ones start sleeping 6-8 hours during the night? 
Oh! I'm breastfeeding as much as I can, more during the night because it's easier for me, I do use formula sometimes.