Q: I want to transfer data from i pad to new ipad air 2 using I tunes back up.

Here's an Apple Support document on it ...

iOS: Troubleshooting encrypted backups

Then you can't use the backup. You can't bypass the encryption. If you don't remember the password you set to encrypt your backups, then it's useless.

There is nothing that you can do to unlock that backup. If you encrypted your backup with a password and you don't remember it, you can never restore that backup.  You have to delete it and start over again.

This kb article explains how to delete the backup. The information is at the end of the article.

Create and delete iPhone, iPad, and iPod touch backups in iTunes

You have to start all over again. If you were to keep using the old iPad and wanted to contNiue to backup, you would have to restore as new after you delete the backup. You will not be able to use this backup at all now. So you will have to start all over with the new iPad without using the encrypted backup.