Daycare and BF

My LO will be going to daycare for 9 hours starting at 3 mo and I'm stressing about how that will work with BF. I plan on pumping but have no idea how much milk I would need to send. She's 2 mo now and she feeds on demand and she feeds very often. Do I need to start getting her more on a schedule? What kind of stash should I have built up before she goes to daycare? Im afraid this won't work out and she'll have to go to formula during the day which I want to avoid.