Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hi
You don't have to uninstall Office 2021 first.
Outlook knows where to look for the old Outlook database file (assuming you're using the same Mac as before). If it can't find the old file it will prompt you to locate it in the Documents folder.
If you are installing Office 2021 it means that you will no longer be able to use Office 2011, as that version is 32-bit and any operating system in which Office 2021 runs is 64-bit. You can never run 2011 and 2021 simultaneously unless you use a virtual Machine in Parallels.
If you plan to stick with just 2021, once you have imported all your Outlook content you can remove Office 2011
How to: Completely Remove Office 2011 From Mac
There are some things you might want to keep from 2011, such as templates and themes. They will work with 2021.