Job interview helpp!?

well i applied at a few job places pacsun, vanity, Claire's and american eagle. i have to take off the 1st 2nd 3rd and 4th off in july for family reasons and the 21st in july for surgery. im not sure exactly how to tell them that when the interview comes around and if i do tell them what should i say to back myself up to as why they should hire me. i also have to take 3 weeks off in december. what should i do/ say? please help first job hopefully? any suggestions? thanks:)