@akangyud
Nuvi cannot be in pre-boot mode and visible in Win Explorer at the same time. It's one or the other, so if it shows as a removable device as in your pic, it's not in pre-boot and cannot enter it. Read the link provided by lolypop000 again, but in 37x0 US/EU the best way is to have the USB lead connected to PC first then plug microUSB into unit and hold on 'G' in Garmin immediately it appears. Also have updater.exe open on your desktop with the *.rgn file already loaded and ready to flash, with 'USB Device' selected. When your device details appear in the USB window you don't have long to start flashing.

Important Note: Be aware that your ID unit has a different HWID to US/EU units which all have 1101. The patching tool and HWID/Software over-rides built into RGN-Tool should not be used or you may brick your unit.