I don't think you're age matters. If I were you, I'd do a search on the Web. Put in words like "cancer" "support" "children" (In French. A French forum would be ideal.)
If that doesn't work, can you talk to your parents? Do they know how scared you are, and that you would like to talk to other kids with parents who have cancer? If you can't talk to them, is there someone at school, like a teacher or a counselor that knows about your mom? Maybe they could help you find a support group.
It's OK to be scared, it's normal, and it's ok to ask for help. I know a couple people that lost a parent to cancer when they were kids. It is hard, and I really believe that it's important to talk about what you're feeling and going through to someone.
Good luck. 🙂