This means that they had come out of Egypt a year earlier. They were beginning their second year in the wilderness. (See: [[rc://en/ta/man/translate/translate-ordinal]])
This is the first month of the Hebrew calendar. It marks when God brought the people of Israel out of Egypt. (See: [[rc://en/ta/man/translate/translate-hebrewmonths]] and [[rc://en/ta/man/translate/translate-ordinal]])
Here "they" refers to the people of Israel. The phrase "came out" means to leave. Alternate translation: "after they left the land of Egypt" (See: [[rc://en/ta/man/translate/figs-idiom]])