As pointed out in the excellent tutorial to which you were given a link, you need to format in a way that Garmin devices will universally accept. Firstly, for nuvi 2x5 devices that's FAT32 only for the internal flash. Secondly, it will read either FAT16 or FAT32 formatted SD cards but not NTFS or exFAT SDXC.

So, being as there are as many ways to format in FAT as there are ways to skin a cat and Garmin is picky you are best to only use RMPrepUSB with a PC for internal formats. Anything else is a lottery, even the inbuilt Windows format tool maybe won't do the job to Garmin's satisfaction.