How can I find recovery key for Apple Account of my iPhone?

The following is extracted from --> Set up a recovery key for your Apple Account - Apple Support (IN)

This gives you more control of your account recovery methods and can help prevent an attacker from gaining access to and taking control of your account. However, if you lose your recovery key and can’t access one of your trusted devices, you’ll be permanently locked out of your account.

Use a recovery key

• To change your Apple Account password using your recovery key, you’ll also need either a trusted device (with a passcode or password) or a trusted phone number.
• If you don’t have access to a trusted device or you’re locked out of your Apple Account, you will need to provide your recovery key to reset your password and regain access to your account. You’ll also need to enter the verification code that is sent to your trusted phone number through two-factor authentication. Didn’t get a verification code?
• When you change additional information about your Apple Account (for example, if you add a trusted phone number), you may be asked for your recovery key.