Reactivate Apple ID

If you deactivate your account see How to deactivate your Apple ID account  https://support.apple.com/en-us/HT208503--"If you request account deactivation, you'll receive a unique alphanumeric access code. When you're ready to reactivate your Apple ID, contact Apple Support, provide your access code, and we’ll help you reactivate your account. If you lose this code, we won't be able to help reactivate your account." 

If you deleted your account see How to Delete your Apple ID Account https://support.apple.com/en-us/HT208504--“While your request is being processed, you can contact Apple Support with the unique alphanumeric access code you received, and we’ll help you cancel your request. After your account is deleted, Apple can't cancel the request, reopen your account, or restore your data.”

From donv's post above:

When you're ready to reactivate your Apple ID, contact Apple Support, provide your access code, and we’ll help you reactivate your account.

You need to contact Apple Support using the link above and give them your code.