Pet store sold me males, insisted they were female now I have pregnant mice

So, I got my first mice several months ago and I was assured they were female so I adopted them with really no second thought trusting they knew. Fast forward to about 2-3 weeks ago I upgraded the cage as I wanted to adopt some more mice. I went through all the usual hoops making sure they bonded nicely. I had read that some mounting was normal in females being joined together as to assert dominance so I let it happen but now the newer mice are visibly pregnant and I dont know what to do. The pet store said “its beyond the 14 day window” and wont do anything to help me out. Whats the best way to proceed here? Ive already separated the pregnant mice from the suspected (highly likely to be) males. Im very lost, very new mouse owner and would appreciate any constructive criticism in my care and suggestions for what to do next. Thank you<3