G'day bluemoon, Happy New Year to you too and welcome to GPS Power.

If you haven't previously updated firmware with GarminExpress or WebUpdater since new then there will be no gupdate.cgd file in .System folder. The gcd files in RemoteSW and the bin files in ExtData folder have nothing to do with the unit software [firmware].

Generally, if a unit has a RWFS partition then the backup will be done to '2' for the microSD and '1' will write to RWFS instead:

[Only registered and activated users can see links. ]

Your nuvi55 will probably have nonvol in region 154 but just copy both regions 41 and 154 if not sure.

To check the firmware version currently loaded to the unit, from the main page press Settings>Device>About and look for Software Version. If you don't have latest version update it with GU or WU or get the latest V4.50 as said by Giomen.

All the info you need is available in [Only registered and activated users can see links. ] too. If not sure how to proceed ongoing, have a look there first Mate.