Breastmilk to Formula Help!!!!

Michelle • Married couple. Mom of 2. #3 on the way👨‍👩‍👧

I have been feeding my baby girl breastmilk in a bottle for 8.5 months. But recently my milk is really slowing down and need to start considering adding in formula. Is anyone going through this? I feel bad that I cant provide enough breastmilk for her til she's a year old. What formulas will be similar to breastmilk to try to use? TIA