What does Exodus 3:18 mean?

'The elders will listen to you. Then you and the elders will go to the king of Egypt and say, "The LORD, the God of the Hebrews, met with us. Please let us take a three-day journey into the wilderness to offer sacrifices to the LORD our God."' Exodus 3:18 - Modern Text Bible

(God predicts the elders will believe Moses, and gives him the words to say to Pharaoh—a request for religious freedom as a first step.)