Where do I get verification code when I do not have any other devices with me?

Kin3010 Said:

"Where do I get verification code when I do not have any other devices with me? App Store login message 'An Apple ID verification code is required to sign in. Type your password followed by the verification code shown on your other devices.' Where do I get verification code when I do not have any other devices with me? Thanks."

Using this Computer with TFA:

You can't. So enable Two-Factor Authentication(TFA) on the iMac.

1. Go Here: Two-Factor Authentication for Apple ID - Apple Support
2. Scroll to: Turn on two-factor authentication on your Mac
3. Proceed form there as necessary

Screenshot:

See if anything here helps.  If necessary, you can use account recovery as explained in the link at bottom of the article.

Verification code - how to get one and sign in with two-factor authentication.