Hope fully this is the only document your will need to see: Get a verification code and sign in with two-factor authentication https://support.apple.com/en-us/HT204974 Below is an excerpt, but read the whole document. See the bold italics below.
“Whenever you sign in with your Apple ID on a new device or browser, you'll confirm your identity with your password plus a six-digit verification code. There are a few ways you can get a verification code. You can use the code displayed on your trusted device, get a text or phone call, or generate a code from your trusted device [see the additional information in the article].” A trusted device is an iPhone, iPad, or iPod Touch with iOS 9 and later or a Mac with OS X El Capitan and later that you've already signed into using two-factor authentication.
“If you can’t sign in, reset your password, or receive verification codes, you can request account recovery to regain access to your account. This link takes you to the next document--one I hope you won't need to use:
Recover your Apple ID when you can’t reset your password https://support.apple.com/en-us/HT204921which you may need to use.
“Account recovery might take a few days or longer, depending on the specific account information you can provide to verify your identity. “After you request account recovery, you'll get an email with a confirmation of your request and the date and time of when you can expect to regain access.” … When the wait period is over, Apple sends you a text or automated phone call with instructions to regain access to your account. Follow the instructions to immediately regain access to your Apple ID.”
