See these documents on Two-Factor Authentication and the quoted information from each below.
Two-factor authentication for Apple ID https://support.apple.com/en-us/HT204915 See this section especially Set
up two-factor authentication for your Apple ID. From this section, "Two-factor authentication is available for Apple ID accounts with at least one device that's using the latest iOS, iPadOS, or macOS. Learn more. You can follow these steps on your iPhone, iPad, or iPod touch to turn on two-factor authentication."
Get a verification code and sign in with two-factor authentication https://support.apple.com/en-us/HT204974
“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.” ...
“If you can’t sign in, reset your password, or receive verification codes, you can request account recovery to regain access to your account. Account recovery might take a few days or longer, depending on the specific account information you can provide to verify your identity.
Before beginning account recovery see:
If you didn't receive your verification or reset email https://support.apple.com/en-us/HT201455
“Not sure where that email was sent? Here are some tips to help you find it.”