Download previous version installer compatible with Catalina

https://officecdn.microsoft.com/pr/C1297A47-86C4-4C1F-97FA-950631F94777/MacAutoupdate/Microsoft_Office_16.55.21111400_BusinessPro_Installer.pkg

Other Versions

https://docs.microsoft.com/en-us/officeupdates/update-history-office-for-mac#release-history-for-office-for-mac