How do I verify my Google Account without my old phone?

He told you to print it out or write it down and store it in a safe place. Which you did, because you knew that day would come, because he said so, right there on your screen, and you had to click the button to hide that screen.

So now go to that safe place, and get the paper. Or you have an electronic copy on your laptop, or a screen shot with the codes on it, on your iPhone. Or if you're smart, you have it in six places, including a friend's house, a security deposit at the bank, and in an escrow account with your lawyer.

In any case, you get those numbers, and then you get to recover your accounts "I no longer have my cell phone number, because I just got out of a 9-month sentence at Rikers Island in New York for running over a homeless person with my car, because otherwise the cell phone company wouldn't violate federal law, and they wouldn't give me my cell phone number back, as long as I pay my monthly bill."

When prompted, enter one of the 8-digit single-use account recovery codes.

When prompted, enter your new cell number.

You then scratch off the 8-digit number, and remove it from the list, since you will never be able to use it again.

At this point you have the option of uncheck the 2FA box, since even having lost access to your cell number would be an heroic task for most ordinary people?

You are not a norm. you are a hero, and heroes can heroically lose access to mobile numbers.

Personally, if you were that kind of person, I would disable 2FA at this point, after having successfully used one of the backup account recovery codes.