If iTunes is asking you for a password to restore the backup, then you created one. Why it is saying it is wrong, is hard to say, except that iTunes is not recognizing what you are trying to type in. Did you use just numbers? Make sure they are correct. If you used letters, make sure you are using the correct case, upper or lower. Make sure the caps lock is not turned on for the keyboard. Otherwise, if you cannot remember that password, you will have to restore the iPhone to factory and set it up as new, not using the backup. And you will have to delete that backup from iTunes, or it will continue to ask for a password. You cannot reset the password.