A Microsoft app for iOS and Android devices that enables authentication with two-factor verification, phone sign-in, and code generation
When you get the security screen, it will have an option to add the app. It displays a QR code used by the app.
if the security screen is asking for a code, then you have already configured google to MFA with an authentication app. It wants to you to use the old app to authenticate, before you can add the new app.
if you no longer have the old app, then you will to go thru account recovery