Can I mix hermit crabs from different stores?And can hermit crabs eat noodles cooked or uncooked?

I have looked at all the sites but I need to know alot more about them and how to take care of them.Also I would like to know if they can have any type of noodles?I got a hermit crab on vacation and im planning to get another one ffrom petsmart can I mix them?And is two enough?