I'm not even sure at what point Moses came to know God. Does the Bible even say?
What text indicates that he knew God before the Burning Bush episode?
Maybe when he fled to Midian when Pharo set to kill him.
Exodus 3:1-4
Moses at the Burning Bush
(Ex. 6:2—7:7; 11:1–4; 12:35, 36)
1 Now Moses was tending the flock of Jethro his father-in-law, the priest of Midian. And he led the flock to the back of the desert, and came to Horeb, the mountain of God. 2 And the Angel of the Lord appeared to him in a flame of fire from the midst of a bush. So he looked, and behold, the bush was burning with fire, but the bush was not consumed. 3 Then Moses said, “I will now turn aside and see this great sight, why the bush does not burn.”
4 So when the Lord saw that he turned aside to look, God called to him from the midst of the bush and said, “Moses, Moses!”
And he said, “Here I am.”