It's the formula. Same happened to my baby. She needs a different type of formula.
Normally breast fed babies don't have problems pooping. I would call your dr and ask them about that.
I did rub her belly move her legs n she went number 2 after that but then again today all day no poop
3 days doesn't sound normal for a baby. I'd check with the doctor. have you tried rubbing her belly and moving her legs?