Yahweh states what would have happened if the priests and false prophets had participated in Yahweh's council meeting in heaven. This hypothetical situation is impossible. Alternate translation: "if they had truly listened to me" (See: [[rc://en/ta/man/translate/figs-hypo]])
In ancient times, God was thought to hold meetings with the angels in heaven. Yahweh is referring to this kind of meeting, which humans could not attend. See how you translated this in [Jeremiah 23:18](../23/18.md).