how do I enable micosoft authenticator on a new mobile phone

Question

I need to use MS authenticator from a new phone. I have set it up, done a backup from an existing phone, done the process of picking up the backup record from the old phone (via iCloud as per the process). Now I am being asked for a QR code for the new phone to complete the process.

Question- Where do I get the QR code?

Note: In the initial set up on the old phone, I got it from the Admin centre since MFA was not enabled. Now it is enabled on the old phone, hence there does not seem to be any provision for getting a QR code.