Once reCAPTCHA keys are migrated to Google Cloud they are no longer considered Classic keys. All reCAPTCHA Classic keys are in the process of being migrated and will be subject to the 10k monthly assessment free-tier (see Billing information). Once migrated, there are no changes required to your integration and SiteVerify will continue to function as-is.

To make sure I understand your question, are you seeing keys in the "Classic Keys" table pictured in this documentation? If so, those keys need to be migrated. Either you can click Upgrade key, which is recommended if you'd like to choose the destination project, or reCAPTCHA will automatically migrate them to a new project shortly.

Please see more details in the Migration overview.