What should i wear tonight ? (concert)?

heyy yea so tonight im going to the backstreet boys /girlisiuos concert and i dont know exsacty what to wear because i've never been to one so like should i wear really nice jeans ans a really nice tank top and you know put on the make up and the jewlery or what ?? ... i'm thirteen and i dont want to wear a short skirt ;P .. um i dont know if you need to know but im skinny ? lol just putting that out there beause different people wear different tjhings.. thanks you !