NEED HELP URGENT!

ok i have an ipad 3, been using it for months already. The thing is when i first started using it i have never connected the ipad to my PC. Now i want to put in some movies in it and so i connect it to my PC, and itunes is asking me whether to backup from my previous backup (from my old ipad) or set up as new ipad. I dont wanna lose my apps and whatnot that i already have in the new iPad. So what can i do?