UPdate- I just saw in my time machine back ups on my mac that i was only using LR 5- i can see a LR 5 cataolg and some folders that i assume go with it somehow.
so this is part of the problem.
I opened my catalog in LR Classic.
Which I thought was OK.
Catalogs are all of the file-type .LRCAT You only need to 'look at' these types of files.
Catalogs will always be accompanied by a 'file' of the Previews : Catalog Name.LRDATA
The 'File Name' of a catalog does not always suggest the Lightroom version. eg. LR-5.LRCAT could be a Classic catalog for v7.4
When you upgrade Lightroom (eg v5>v6, or v6>Classic7 ) Lightroom adds a number suffix to the catalog name.
eg. Catalog.LRCAT becomes Catalog-2.LRCAT
If you upgrade an 'old' catalog multiple times you will get catalogs with increasing suffix number. -2 -3 -4 -5, etc. So do not keep opening an 'old' Lightroom-5 catalog. It appears you have been doing this.
The mB size of a Catalog.LRCAT file does not indicate the content or "latest" version. Recent versions of LR-Classic compress the catalog more aggressively. "highlighted in blue is 1.32gb" is NOT the catalog!- it is a Preview cache- ignore.
You 'largest' catalog appears to be this one in the screen-clip, BUT - only YOU can determine which of the .LRCAT files contains all your photo data. (as the MB size does not tell!)
So if you open a catalog and it asks to "upgrade" do not, Just exit and move that Catalog out of your working folder to another location.
I also note you may be using this drive for Backups. You should specify another physical drive location for Catalog backups.