No you don't need any documents. Bring an extra resume just in case, and that's all you'll need. But bring your wallet with you anyway. If they decide to hire you they may need your sin number that day, or when you come in for your first shift. But they'll ask you what department you want to work in, why you chose k-mart, future plans, like what you want to do in five years, plans for school, availability, experience, etc. All those questions. If you've left anything recent they'll probably ask why. Also if you're a people person too. Just the usual too, especially if you've had experience working in cash. Just dress nice, casual nice will do, like a nice top and bottoms, arrive early for the interview too. Like ten minutes or fifteen at best before and tell them you're here for the interview at whichever time frame. Make eye contact, smile, don't fidgit if you can help it, and try and sit back and relaxed. Like back straight but try not to look too nervous. If you do it's ok, a lot of people understand nerves can get the best of us at times :) Just breath, relax and go in with confidence :) Speak clearly (something I don't always do). But you'll get better at it as time wears on :)
Try asking yourself the questions you may think they'll ask, or get someone to do a mock interview as a test, and ask your family too, they can tell you what questions to expect. They're all pretty basic and most of them routine from job to job, but the most important thing to remember is first impressions are very important :) Don't stress about this, these are just tips on what to expect, and to help show a person that you are confident, even if not at %100. You want to prove you are, and can do your job, which isn't hard :) Everyone makes mistakes and you'll be a pro at it in no time :)