Hi Hannah, In France, there is no official degree to become a translator.
Even though, you should apply for ESIT or ISIT in Paris which are the best schools to become a translator.
Then, some masters are available around France (4 or 5: Toulouse, Rennes, Montpellier, Grenoble for example)
Usually translators make translations into their own language so on top of having a great level of language for the source text, it is important their production (target language) is written correctly. Hope I helped.