Formula question

Nicole

My LO is 5 months old and I’m going back to work in a week. I’ve been breastfeeding and have been weaning him off to start formula. I’ve gotten so used to breast milk storage rules and don’t always know how much to take out for him when I give him a bottle. So I’ve started to look into formula. This might be a stupid question but what does everyone use for water that you mix with formula? I’ve read mixed things.