Microsoft suite is gone after the latest software upgrade. How do you get it back ?

If you are talking about upgrade to Catalina and you were running an old 32 bit version of Microsoft Office you will need to upgrade Office to a 64 bit version. Office 365 and Office 2019 are 64 bit.

To add, the latest version of Office 2016 is compatible with Catalina, so if you have Office 2016 you can simply update the apps (but Office 2016 is no longer available for purchase, you'd need to buy Office 2019 or subscribe to Microsoft 365).