I'm new to the Garmin world and in general it's been a while since the last time I updated the maps on a GPS and it was a TomTom, I saw the "how to" forum but it is confusing as I notice also on the maps section several different files and not sure which file type ( MS lock, ImgUn, 3DUn, D3478230A_JVC_nuvi 40-50, JVC, SID, etc, etc) applies to my device and which to newer more advance devices, please any help would be highly appreciated.