How do I transfer my iCloud info to a new account without losing saved info
How do I transfer my iCloud info to a new address when I forgot password
iPhone XR, iOS 15
You deal with the forgotten password issue and continue to use the old account. If you want to use the new account with the information, transferring is not easy and will require you be able to get access to the old account anyway so you might as well just use the old account.
Click on this link to read what to do "If you forgot your Apple ID [Account] password" --> https://support.apple.com/HT201487
or go directly to this link --> http://iforgot.apple.com/
Also read about "What to do after [or before] you change your Apple ID email address or password" --> https://support.apple.com/HT204071
If you still need help:
Contact Apple for help with Apple ID account security "This article provides country-specific Apple Support contact information for customers seeking help with their Apple ID password or other security-related issues." --> https://support.apple.com/HT204169