Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Dear John McN
Welcome to the Microsoft Community! We are happy to assist you.
Understanding your question, you want to upgrade your Office 2019 to Office 2021.
In order to better help you, would like to confirm some questions with you:
Is the system you are using Windows or Mac?
You mentioned that you have created multiple contacts and calendar files with Office 2019, using outlook?
What specifically is your Office 2021 subscription? (e.g. Office 2021 Professional Plus)
Since they are all one-time permanent subscriptions, if you want to safely upgrade from Office 2019 to Office 2021, we recommend that you still choose to uninstall and reinstall Office. If you uninstall Office before installing a new version, Office files will not be deleted, but if your version of Office includes Outlook, you may want to back up the Outlook data files. See **** Find and transfer Outlook data files from one computer to another - Microsoft Support
For more details, you can refer to:How do I upgrade Office? - Microsoft Support
If you are worried about losing your files and data, you'd better backup your important data before uninstalling.
Thank you for your understanding and patience. If you have any other updates, please feel free to let me know, thank you.
Jennie | Microsoft Community Support Specialist