With Catalina, do i have to upgrade to Office 365 or can i stay with Word

Word is part of Office 365, but if you have a copy that works with Catalina, then you do not have to upgrade. To be sure See App Compatibility Table - RoaringApps.

Microsoft Office topic - Office 2016 has an update, earlier versions cannot be updated. Either start using Office 365 or do not upgrade your macOS and continue using the old versions.

https://discussions.apple.com/thread/250281343