These pipes were not mentioned in the previous description of Zechariah's vision. It is possible that they are connected to the bowl on top of the lampstand and provide the oil with which the lampstand burns.
The angel asks this rhetorical question to emphasize that Zechariah should have known what these things mean. This question can be translated as a statement. AT: "Surely you know what these are." (See: [[rc://en/ta/man/translate/figs-rquestion]])