It doesn't exist. e.g. Dinosaurs do not exist anymore. Dinosaurs no longer exist. (same meaning)

Kai. It would sound better to say this: "Therefore, translators must know whether it is more appropriate for their target audience." You could put "hence" where you did but it sounds a bit strange. "However" is more commonly used than hence. It also sounds more natural/fluid to put it at the beginning of the sentence. You also put a few different words that mean roughly the same thing: adequate, suitable, and acceptable. I would just choose one and keep it simple (you'll see that I chose "appropriate" which I think is what you're going for).