They decide to consult with the prophet Elisha (2 Kings 3:11-3:12)

“King Jehoshaphat said. ‘Is there no prophet of Yahweh here, through whom we may inquire of Yahweh?’ Then one of the servants of the king of Israel answered. ‘Elisha son of Shaphat, who used to pour water on the hands of Elijah, is here. King Jehoshaphat said. ‘The word of Yahweh is with him.’ So the king of Israel, King Jehoshaphat, and the king of Edom went down to him.”

King Jehoshaphat was always looking for the prophet of Yahweh to tell him what to do as in 1 Kings, chapter 22, when he was with King Ahab. One of the servants of the king of Israel said that the prophet Elisha was there. He used to pour water on the hands of the prophet Elijah. King Jehoshaphat said that the word of Yahweh was with him. Then all 3 kings went to see Elisha.