I’ve never done this so I’m brainstorming here.
Very, very best would be if the pups could be housed outdoors during the day. All you really need is a lot of fence panels and a spot with some shade throughout the day. Bring them in overnight and provide newspaper or pee pads. They’ll quickly learn it’s more pleasant to potty outdoors and start going all night.
Otherwise, I would pen the puppies as near to the outside door as possible. At specific intervals (following nap times and meal times), open the pen and make a big fuss outside so they race out to see what you’re doing and don’t stop to eliminate indoors. Obviously this would require a yard with puppy-proof fencing since you can’t keep track of 9 pups at once. It would help if you had another person there to spot who has done their business and who hasn’t so you can reward appropriately and know when it’s safe to take them back inside.
Good luck! I’d love to hang out with 9 puppies but I wouldn’t want to house train them!