Comment by ck2

not sure if this will help you but there is a neat website that allows you to build free maps for older Garmin models that didn't have them at first like Fenix5

https://garmin.bbbike.org/

1990s is going way back though, they didn't even have mass-storage mode then, it was their proprietary "garmin mode" for usb which only things like BaseCamp can talk to