how to backup all saved tracks
You can sync data from your GPSMAP 66i to the Garmin Explore website using the Garmin Explore app. Instructions are here: Syncing a GPSMAP 66i/86i/86sci With the Garmin Explore Website and App
You can also…
Connect your GPSMAP 66i to a computer and copy the files in the Garmin\GPX folder (and subfolders) on the internal storage to your computer. This folder also contains any waypoints you have on your device…