I have two new six week old kittens Ive had them for 24hr and they have not made a bowel movement?
I have been feeding them an expensive hard cat food with warm milk mixed in and they have eaten quite a bit.
One of them has been drinking water but the other won't touch it I tried making sure we always had fresh water for them changing it out every few hours but I still can't get it to drink anything but the milk in the food can anyone help?

First stop the millk. Milk can cause GI upset. Are they still eating? If so, give it until tomorrow (I am assuming that you posted this Sunday afternoon-ish and mean they haven't gone since Sat.) If they are still eating, drinking, and nothing by tomorrow am, I would at least call your vet. If they do go, great. If they are having trouble eating the dry cat food with no milk, you can 1) add water to make it softer for them or 2) provide some moist cat food for a short period so they are eating and getting extra water, too.
Have they been dewormed? If not, I advise having a poop sample checked in the very near future (as soon as they make one! ) and deworming for any parasites they might have.
Good luck.