Bulk importing tracks/activities into basecamp

Have you tried using the Basecamp import function, which will import fit files?  No idea if it will bulk import as I don't use fit files.

Hmm, just submitted a reply and it is not showing up here...so, trying again.
I tried your suggested solution (thanks!), but out of my 2892 or so *.fit files under "DI_Connect" from the data dump, and doing a select all, it seems to load only a tiny fraction, since basecamp only shows the last couple of months of hikes opposed to 8+ years worth of hikes. 
I also tried converting the fit files to gpx, but that can be done only 1 file at a time and it failed for the very first one I tried due to an out of memory" or so error.
Seems like Garmin is not offering a tool to a) either plot/show all activities on a world map, or b) allow a proper gpx bulk conversion, c) or bulk import of all files in basecamp. 
Are there any other options/tools?

Edited: One more piece of info: when I bulk load the fit files into basecamp, it seems to only load files with a few hundred Kbytes or more (but it cannot be those are only from 2024...need to dive deeper; edit: there are only 88 files with more than 100kbytes out of the 2892 and that is approximately the number of files after importing into basecamp listed under Library/My Collection).
Many of the small ones are not loaded it seems at first sight...maybe they are corrupted, but why would Garmin offer those in the bulk download and how can I test that theory (and why only hikes working from this year)? 

Edit 2: I found a tool that may be able to batch convert fit files to gpx: Automated batch conversion of Garmin FIT files to GPX in Windows » childs.be  will be testing it soon.

Your watches stores your activities in FIT format, not as GPX. They also convert GPX files to FIT after you upload them, that's why the majority of the files are in FIT format. The GPX files that you have uploaded to Connect (and possibly only those uploaded to the web version of Connect) will remain in GPX format.

Also note that just a small number of the FIT files contain activities, the other files probably contain metrics (I did a test with my export; about 3% of the FIT files contain activities)

I used JaVaWa RTWtool to convert a folder with 300 FIT files, resulting in 9 activities. Don't try them all at once, maybe 1000 files at a time.

Save the result in GPX format and open that file in BaseCamp.

Thanks - I used https://www.childs.be/ to batch convert the *.fit files and it worked. However, results are the same as when directly loading the *.fit files into basecamp. That means that I only see 2024 activities in basecamp - not sure why. When I requested data export from the Garmin data management site I did not see an option to set the date range,,,,maybe I am missing something here.
Maybe I should try your tool too....will try tomorrow.

The tool you found is based on GPSbabel, it can convert FIT files but additional data like temperature, heartrate or cadence will be lost.

Your number of FIT files is very low though, I've got 27000 files here for the last five years, almost 10 times as much as you have...

Thanks - you got a point. I suspect, for some reason, I did not data dump all activities/racks etc. Will try again,