from another forum:

Instead nothig to do for me!
If I put folder LEX_PKG (with his gmapsupp.unl) in my SD-HC 8GB the Nüvi 1350 don't see anything, and if I put folder LEX_PKG under .System folder Nüvi 1350 told me that Garmin Language Guide is locked!!
Anyway with:
ID Nüvi 1350 as 3623822780 with 4.50 firmware
MapId=900
PID=2
RgnID=0
VenID=0
I have unlock code xxxxxxxxxxxxxxxxxxxxxxxxx
What's wrong?

reply:
Open rar click exstract all (folder.System and folder Garmin) to SD,open keygen generate unlock code.
Go to SD card folder garmin open gmapsupp.unl paste unlock code,save.Run nuvi and garmin language guide work 100%
(thanks lolypop000 )