i can´t restore my backup form itunes the password is the problem how can i get it

You can't recover it, you have to erase the de id and start over again. You have to delete the backup in iTunes as well or the phone will continue to use that encrypted backup.

There is no way to recover your information or turn off Encrypt Backup if you lose or forget the password.

About encrypted backups in iTunes - Apple Support

You can't use an encrypted backup if you don't have the password. If you forgot your password, the only way to turn off backup encryption on your device is to erase your device and set up as new. Erasing removes all data from your device. If you don't want to erase your device, restore from an iCloud backup instead.