I have an interview at Target tomorrow, tips please?

I am 16 and this is my first job interview. I checked on the website and they said to wear a suit…I don't own one but is a longish skirt okay with a nice blouse? Also, I do not have a resume because I applied online. Should I put one together? I only have babysitting jobs I could put on there. Cover letter as well? Also, what kind of questions will they ask? What should I say? Do I say a statement first or let them talk? Any suggestions will help a lot (especially coming form a Target employee). Thank you!