A few days ago asked this question with title «How many people left Egypt?» and the given answers state over 2 million persons.
Considering that in Exodus 16:1 (NASB)
Then they set out from Elim, and all the congregation of the sons of Israel came to the wilderness of Sin, which is between Elim and Sinai, on the fifteenth day of the second month after their departure from the land of Egypt.
we read that mana appeared over 30 days after they left Egypt...
How could they survive that long?