Your old iPhone is lost in which the Apple ID was signed in , if the account was set with 2FA and password is known see the method .
The Apple ID say example1@icloud.com exists on server and you know the password and its account credentials , however that is signed in the device iPhone / Mac / iPad .
If you don't remember the trusted number and yet it is verified in the account , visit your cellular service centre with personal identification proofs , the number can be obtained from them .
If the account is set with two factor authentication from iPhone .
Issue a sim on behalf of the same number and insert the sim Set up cellular service on iPhone - Apple Support
In a new iPhone that is purchased Turn on and set up iPhone - Apple Support
The Apple ID and password is active so is the 2FA active on the iCloud server , once a new trusted number is added the code will start appearing on the new trusted number , and the person can access the account .
See the article Get a verification code and sign in with two-factor authentication - Apple Support
Then access the account and remove an old inactive verified number from the account .
Go to your Apple ID account page and enter your Apple ID and password.
In the Security section, click Edit.
Click Add a Trusted Phone Number.Â
To add a number, enter the phone number and verify it with a text.Â
To remove a number, click cross sign next to the phone number you want to remove.Â
Note : you don't need account recovery from the server as Apple ID and password are known to you How to use account recovery when you can’t reset your Apple ID password - Apple Support
If the account was set up with secondary authentication in which three answers for respective questions , rescue mail address and its password , date of birth is added , simply sign in with account credentials on new iPhone Sign in with your Apple ID - Apple Support
Regarding you Apple ID created as xxxxx@gmail.com with its password can't be established in your old appleid account , as for different mail address the credentials like password and other data can't be same and reused .
See the article https://support.google.com/mail/answer/56256?hl=en