encryption password for backup

If you stored your iPhone backups locally on a Mac here is something that might work.

Applications>Other,>Key Chain Access

search for "backup"

Double click "iOS Backup"

Check show password

Enter your computers login password. It should then reveal the password you used to encrypt your iPhone backups

(I can't remember if iOS backup is the default name of these files or if there is an option to use different name. You may have to search for another term if you named your file differently)

If this doesn't work for you, you can also check to see if you stored any backups of your iPhone in iCloud.

You can't. If you can't remember the password for an iTunes encrypted backup, you can't restore from it.

That's the whole point of encrypting the data.