I have DriveSmart 61 LMT-D and it only says system software missing.
After plugging it to the pc Garmin Express does not see it however it is in the device manager.
I read similar topic here so i guess the navigation is in the preboot mode but I have no clue what are the next steps and how to fix it.

What's wrong is that the firmware (Garmin calls it "the System Software") is either missing or corrupted in region 14 (hex 0x0E). That may be a simple fix or it might indicate that there is physical damage to the flash memory which involves region 14.

Because the device has defaulted to preboot mode, you can try re-flashing the firmware as an RGN file using Updater.exe. The reason GarminExpress doesn't see it is because it reads devices in Mass Storage Mode/Media Transport Protocol only not in Garmin Mode or "preboot" mode.

I realise you posted a few weeks back and may now be sorted but if you need further help re-flashing it with Updater.exe post again and i'll make a kit for you to use.