I don't remember my backup password

If you have a Mac and backed up your iPhone to that Mac then you may try the following:

Check the macOS keychain

If you use a Mac and configured the backup password on that Mac, your computer may have kept a record of the password in its keychain.

You can check this by loading the "Keychain Access" app that comes with every Mac.

1. Launch Keychain Access by opening Spotlight with ⌘ Cmd + (space), typing "Keychain Access", and then hitting ⏎ Enter.
2. Click "Passwords" in the left-hand category sidebar.
3. Type "backup" into the search box in the top-right of the window.
4. View the saved password entries by double-clicking on results named iOS Backup or iPhone Backup.
5. Check the "Show password" box and the password will be displayed.

Axel F.

Unfortunately, you will need the secure backup password that you created to restore your iPhone from that backup file. Fortunately, you do get unlimited tries to guess the password.

Axel F.