I don't think the Serbs are that active in France nowadays. Maybe in theft. Serbs are more active in the Scandinavian countries, Netherlands, it's neighbouring Yugoslav countries and Austria. In those countries they still are involved in a wide range of criminal activities such as drug trafficking, arms trafficking, contract killing, fraud,...
Maybe they're also still strong in Germany but I'm not really sure about that, since Germany in recent years is home to Albanian, Turkish, Russian and Vietnamese mobs and Germany has also seen the rise of particulary brutal and increasingly powerful criminal organizations composed of Mhallami people such as the 'Miri clan'.