Some of this is duplicating what
@sussamb has said and what you have already discovered. But there is no harm in completing the picture for anyone else looking in. This info is drawn from my XT - I suspect that the 396 will be very similar.
On the XT the maps are located in the Internal Storage/.System/Map
You need to enable the System files to be visible on the Zumo.
The filenames are grouped - It helps to sort them into name order.
There may be 2 or 3 files that have the same name with different extensions (.img , .gma, .unl)
.img is the actual map, .gma and .unl are to do with unlocking the maps.
My Lifetime maps do not have a .unl file.
- Maplist.jpg (23.68 KiB) Viewed 2296 times
For the XT, the Europe maps are split into two:
CN Europe NTU 2022.20 All North
CN Europe NTU 2022.NTU All South
- MapList XT.png (40.69 KiB) Viewed 2296 times
In Basecamp, when the Zumo is connected, the drop down list for the map selection will show the the maps that are on the computer together with the maps that are stored on the Zumo. You can select which maps you wish to use from the drop down list.
- Maplist BC.jpg (32.56 KiB) Viewed 2296 times
Unhelpfully, there are three Europe NTU 2022.2 Maps listed - all with the same name. It is impossible to tell which one is which- but one of them will be the map that is on the computer. Two of them will be for the north and south maps for Europe on the Zumo. You have to guess.
If the Zumo isn't connected, I see a very much shorter list with only one Europe NTU 2022.2 map listed.
If you select one of maps that is not on the computer, you will get a warning indicating that you have selected the map on the Zumo, and that you already have the same map installed on the computer. In my case, the bottom one of the three with the same name is the one on the computer.
- Map Duplicate.jpg (17.49 KiB) Viewed 2296 times
When the Zumo is connected, you can tell which filename in the Internal Storage/.System/Map folder is associated with which map buy using the Internal Storage information in the left hand Pane in Basecamp. The Europe maps are shown as a pair, and no indication of which map is north and which is south is given. But they come as a pair. But both files are larger than 2GB and I guess that the internal storage is not able to handle files larger than 4GB.
- Map Pane.jpg (44.5 KiB) Viewed 2296 times
Apologies for over doing this - I think I'll put it into the notes on the XT for future reference.