@Ken St John , Sorry for the confusion!
Currently you have two servers: Old server (1) and a new server (2) - Both these servers are independent.
For now, you want to delete the backup data from Old server (1), to do so, follow the instructions from this article - https://video2.skills-academy.com/en-us/azure/backup/backup-azure-delete-vault#delete-protected-items-on-premises
To register a new server (2), install MARS agent and register the server to the vault. Here are the steps to follow - https://video2.skills-academy.com/en-us/azure/backup/install-mars-agent
If you are planning to install Azure backup server, please follow the guidance from this URL - https://video2.skills-academy.com/en-us/azure/backup/backup-azure-microsoft-azure-backup
Hope this helps!
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