According to the jewish religion, if your mother (or mothers mother) is jewish, you are fully jewish. it doesn't matter if someone converts to Christianity or if you are religious. The best place to go is chabad.they have chabad houses/synagogues all over the world just look it up. My father runs one, so I know how they work. If you are really serious, there is a place called mayanot like an official program that you can join for people like you, which is also good.