Updating Catalina 10.15.7 to OS12.0

I have a 27" 2013 MAC Desktop with Catalina 10.15.7. I noticed none of my Microsoft 365 applications were active. When I tried to update the system says that we need MAC OS 12 or newer to run Microsoft 365. Can you please give me advice? Hopefully I dont have to replace this unit....

Regards

Daryl Holmes