What kind of computer do you use? Is it a Windows or a Mac?
Here's an official guide from apple, I hop it helps you.
iOS: Importing personal photos and videos from iOS devices to your computerhttp://support.apple.com/kb/HT4083
BTW, here's also a video guide to help you transfer files from iPad 3 to computer with iTransfer.http://www.youtube.com/watch?v=lDVtLpWWjrs