To recover an old Yahoo account or Help 1-888-303-0967, go to login.yahoo.com/forgot and enter your old email address. Follow the prompts to see if Yahoo recognizes the account and offers recovery options. If the account is still active and you have access to a registered recovery method (like an old email or phone number), you may be able to reset the password. However, if the account has been inactive for more than 12 months, Yahoo may have deleted it according to their policies. If so, the account and its contents cannot be recovered.
https://hub-info.mystrikingly.com/blog/retrieve-my-old-yahoo-account