
Crate training puppies can start once they are almost weaned. Have you a whelping box with a door that the puppies can get out of ? if you do you can start leaving it open for them to explore in to a"freedom" type puppy pen once they have their eyes open & are moving about freely, then you can remove the whelping box once they are say 4 weeks old & replce it with a crate big enough for all of them.
The puppies won't be able to see properly until their eyes have been fully open for a few days, so won't be aware that they are in a crate until they can see it.
I used to pop the puppies in to large plastic storage boxes(the ones that stack together)when they are very small & I clean out the whelping box. Then when they are old enough pop them in a puppy freedom type pen with access to the whelpng box. Then when I replace the whelping box with a crate & with "vet bed"in to encourage them to use it as their bed & so they can be contained in the crate when they sleep at night & treat it as a sleeping place during the day.
This has worked well with Wukee & his litter mates(I didn't breed them but their breeder uses this method)