Translation:We are ordering tickets for a classical music concert.
Also в. It corresponds to whichever is used for the prepositional case, so:
"at the concert" = "на концерте" == "tickets to the concert" = "билеты на концерт"
"at the theater" = "в театре" == "tickets to the theater" = "билеты в театр"
A lot of things you buy tickets for happen to use на: концерт, спектакль, футбольный матч, самолет, поезд, and more. But you'll see в for театр, кино, цирк, and others.
Thank you! I wrote this comment a while ago, so I have learned much more since then, but I am still very grateful for any answer to any question, especially a specific answer. And yes, for sake of future comment readings, I will edit my comment. That was just a silly spelling mistake. :)
Yes, accusative. If you're familiar with Monty Python's Life of Brian, there's a good Latin grammar scene where the guard says "that's motion towards, isn't it?..." "accusative, accusative!" Anyways, helps me remember. You can think of this as "a ticket (for admittance) to the concert."