error with French language code fr-FR

I have installed a French translation, but when I try to add the language in the backend, instead of showing fr-FR, the dropdown menu show "french" as language code. Of course that does not work, see: http://www.imc-world.com/
I have tried installing other translations, but that did not fix the problem. Is there a way to change "french" to "fr-FR" and in which file do I change it?

Probably, you just have to change the name of the french language subdirectory, and also change the title/name of the MAIN language File, sitting in the Language main Section. It about looks like on the (manually manipulated) image below, I have no french Languages installed , to make sure.
But since no strict rules seem to exist on this, (like on many OC related things!) it mostly depends on the Language File Creator, on, how it's been written. Sometimes, Extensions even add their own named Language Subdirectories for this.
Ernie

I have changed the name of the directory to /opencart/catalog/language/fr-FR, and the php file in it was named french.php, so I renamed that one to fr-fr.php as well. Done the same in the admin directory. I deleted the french language in the backend settings and re-installed it, but no change, frontend still looks the same and when I change to French in the frontend, it is still showing in English.

if the directory is: /opencart/catalog/language/fr-FR,
the MAIN language file name would either be fr_FR.php, or then fr_fr.php, I guess.

But, whatever you do, after any Doings, always clear out the Modification Section as well as the 2 VqMod/xxx.CACHE files and the entire VqCache File Content, to make sure, it displays latest Values.

Ernie

the php files for the other languages are all xx-xx.php, ´not xx_xx.php, so this is not the problem.
I have now reset the modifications, but where do I find those other files and that directory?