Stupid formula question

Hey mamas. Up until today I've been EBF my little. She's having some tummy problems and is seeing a pediatric gastroenterologist... he wants to try her on a specific formula for a week and see if it helps.

How many ounces do I make? Is it the same as breastmilk? Why does it smell so bad?? Should I just stop pumping and do formula from now on?