Outlook 16.23.1 not searching correctly on Mojave 10.14.4

I've had intermittent problems where the search function in Outlook on my Mac would stop working. In the past, I had a reliable fix that I found somewhere online; I ran the following in Terminal:

mdimport -g ‘/Applications/Microsoft Outlook.app/Contents/Library/Spotlight/Microsoft Outlook Spotlight Importer.mdimporter’ -d1 ‘/Users/USERNAME/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile’

... where USERNAME was the home directory name on my Mac. This took a while to run, but worked like a charm every time.

But I recently upgraded to Mac OS 10.14.4 (Mojave), and apparently this command is no longer supported in Terminal. Now when I try to run it, I get the error:

'-g' no longer supported. Importers may only be tested by installing them.

To be honest, I don't really know what the "-g" parameter means. Any ideas on how to resolve? I'm a bit out of my depth here and don't want to do something that makes things worse.