Hi,
Open this PHP file:
/templates/flexible_sportmart/html/com_virtuemart/productdetails/default.php (or flexv2.php depends on what layout you are using for product details page)
and find this line:
js.src = "//connect.facebook.net/en_US/all.js#xfbml=1&appId=115329165206253";
and replace it with this:
js.src = "//connect.facebook.net/fr_FR/all.js";
then the Facebook Like button will be in French.
Regards.
Support