Jesus knows that John's authority comes from heaven, so he is not asking for information. He asks the question so the Jewish leaders will have to tell what they think to all who are listening. This question is rhetorical, but you will probably have to translate it as a question. Alternate translation: "Do you think John's authority to baptize people came from heaven or from men" or "Was it God who told John to baptize people, or did people tell him to do it" (See: [[rc://en/ta/man/jit/figs-rquestion]])
"from God." Jewish people avoided referring to God by his name "Yahweh." Often they used the word "heaven" to refer to him. (See: [[rc://en/ta/man/jit/figs-metonymy]])