You have a cycled fry tank, in addition to another tank?....if so, put the shrimp in the fry tank, until they mature...then add to the other tank
Cherry shrimp can run as much as 2 or 3 bucks a piece, amanos even more (if that's what you have; amanos are difficult to breed, they hatch into a larval stage, that needs brackish water to survive)...I'm betting they are ghost (glass) shrimp, which are easily bred, and usually used as feeders
Whether or not you let the shop know about the hitch hikers is your choice