How many times did moses go on the mountain to meet God and how long did he stay each time?

Answer 1

Unlike any other prophet, ever, in the Old or New Testaments, God spoke to Moses Face to Face.

Every other prophet, from Adam all the way up to Jesus and beyond him to John who wrote the book of Revelations, we are told that men and women heard the voice of God in dreams or in visions of one sort or another. But nowhere else in The Bible is there anyone else who is described as speaking with God the way that Moses' conversations are described.

In addition, we do not know how many times God and Moses spoke with one another. Although there are clearly a number of specific instances that are described the books of Exodus, Numbers, Leviticus and Deuteronomy, the text also states things such as "every time Moses went into the tent of meeting the people would fall on their faces". Phrases like this indicate that meetings between God and Moses happened so frequently and on such a regular basis that it was too numerous to keep track of.

Answer 2

Twice, once to meet God and get the 10 commandments, and second to get them again because he broke the tablets previously. It isn't specified for how long each time though, but the first time was long enough that the Hebrews thought he might be dead and began worshipping other gods, (hence Moses breaking the tablets on his return).