which passcode required in order to remove the itunes encrypted backup

I think you are needing two different passwords/passcodes. One to get permission to connect to the phone and the other for the backup.

To learn about encrypted backups [of] your iPhone, iPad, or iPod touch, click here --> About encrypted backups on your iPhone, iPad, or iPod touch - Apple Support

- To protect backups of your iPhone, iPad, or iPod touch on your computer, you can use password protection and encryption.

- When asked, make a password. Create one that you'll remember or write it down and store it safely, because there's no way to use your backup without this password. If you forgot your password, learn what to do —> If you can’t remember the password for your iPhone, iPad, or iPod touch encrypted backup - Apple Support

See also Disable iOS backup encryption - Apple Community. In particular:

If you have forgotten the password, or were not aware that encryption had been enabled, consider that it might be any computer, Apple ID, Wi-Fi password or device PIN that you've used in the past, working from the assumption that you might have reused a common password that you were using when encryption was first activated. See About encrypted backups on your iPhone, iPad, or iPod touch - Apple Support for details.

tt2

If iTunes is currently performing encrypted backups of your device then you set a password at some point in the past, whether you recall doing so or not. See my post above.

tt2

See the second article to which I provided a link.