Using the Office Deployment Tool, you can upgrade an existing installation of Office 365 or Microsoft 365 Apps from 32-bit to 64-bit without a massive uninstall and reinstall process.
On my machine this took about 5 mintues to do from start to finish.
Download the Office Deployment Tool
Start by downloading the Office Deployment Took from the Microsoft Download Center
Extract that to a local or network location that the system can access.
Create the XML File
You will need this XML code in a file to tell the Deployment Tool to perform an Arch Migration.
Copy this and save in a file called 64ArchMigrate.xml
<Configuration> <Add OfficeClientEdition="64" MigrateArch="TRUE"> </Add> </Configuration>
Run the Deployment Tool
In a PowerShell or Command Prompt running as Administrator, run the following command from the extracted location:
setup.exe /configure 64ArchMigrate.xml
Any opened applications will need to be closed, but this will automatically upgrade the architecture from 32-bit to 64-bit for all existing Office 365 or Microsoft 365 Apps installed.
For more information on this process, check out the Microsoft Docs article: