It is not possible to merge Apple IDs.
To see how to 'Get a verification code and sign in with two-factor authentication', click here --> https://support.apple.com/HT204974
- Use a Trusted Device: Mac, iPhone, iPad, Watch. Code is either generated automatically or manually using Settings on the Trusted Device.
- Text or phone call to a trusted telephone number (also landlines).
- Get a code from an Account Recovery Contact --> https://support.apple.com/HT212513
Manage and use your Apple ID - Apple Support
Update trusted phone numbers and devices that you're currently signed in to with your Apple ID.
Contact Apple for help with Apple ID account security - https://support.apple.com/HT204169 "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues."