If the guide mentioned above (http://gbatemp.net/threads/a-gba-save-converter.53867/#post-694180) does not work, you have to re-check your save file with hex editor. I have used to download one .GSV save file from GameFAQs. But when I opened that file with HxD, there are only trash data.
Here is a download link to this save, for reference: http://www.gamefaqs.com/gba/918915-pokemon-firered-version/saves
GAMEBOY ADVANCE GAMESHARK SP SAVE FILE (NORTH AMERICA)
Save Game File 05/16/05 sleep_mode 33K
Full Pokedex, All Badges, Name: Max, Money: 342,750