How to tie .FIT and .MP4 to each other VIRBX

I have a VIRBX which I have been using on my motorcycle for years. I took a trip to Alaska with it and thought I could use the GMetrix data to tie the location of the .MP4 file to the locations in the .FIT file. I have successfully decoded the .FIT GPS Coordinates but am having trouble figuring out which .MP4 files are associated with which .FIT files and the associated data. Does anyone know how Garmin associates which .MP4 files with the specific .FIT files?

Thanks,