Starting with LR 7.3, the new location for develop presets is /Users/username/Library/Application Support/Adobe/CameraRaw. When LR 7.3 starts, it converts any old-style presets it finds in the old location (ending with .lrtemplate) into the new-style format (ending in .xmp) in the new location. The old .lrtemplate files are renamed to start with "~" to indicate they've already been converted.
Your screenshot shows User Presets collapsed -- if you expand it by clicking the black triangle, are your presets in there?
If not, it may be that all of the .lrtemplate files in the old location are still prefixed with "~", so LR 7.2 sees them just fine, while LR 7.3 thinks they have already been converted. (But the converted ones in the new location didn't get restored after your reformat.) Try renaming all of the old .lrtemplate files to remove the leading "~" or "~~" and then starting LR 7.3 again.
Also, the most recent version is 7.3.1, which fixes some (but not all) of the preset bugs introduced in 7.3. So make sure you update to 7.3.1 before doing anything else.
Thank you! I had missed this news. I went in and mass removed the ~~ and then updated Lightroom and it ran through the updater and now works great.
Thanks for that!