These are the language files to have USB Loader GX translated to your language. You can download them from here, use the download languages option of the loader (somewhere in the settings). The update all function also updates to the latest language file.

The thread about the translation is
http://gbatemp.net/index.php?showtopic=155252

Report there any translation problems or offer your translation

You need to input the full filename in the settings for the translation you want to use