Nephi tells us of the passage of time only that this next event occurs after "the space of many days." While not critical to Nephi's purposes, it is yet instructive to know how the Lord dealt with the Lehites. Nephi is very clear about their struggles in coming to Bountiful (1 Nephi 17:1) and the contrast between the hardships of the trail and the abundance for which Bountiful was named. It is comforting that after eight years in the wilderness, the Lord allowed them "the space of many days" to rest and recover before announcing to Nephi that they were to build a ship, and leave on yet another difficult journey.
After this indeterminate number of days, the Lord speaks to Nephi and tells him to "get thee into the mountain." Nephi does not specifically say that the Lord told him to cry unto the Lord when he got there, but that was clearly the implication. Why would the Lord make such a request? In order to give the request, the Lord was already in communication with Nephi. Why make the extra request to go to a mountain and essentially pick up the conversation there?
The answer lies in the sacred nature of mountains. Mountains symbolically serve in the place of temples when there are none, based on the Hebrew conception of the mountain. The mountain was considered to have its roots below the ground, reaching into the primordial waters. The summit symbolically reached the heavens, and thus the mountain was an appropriate location for one to meet with their God.
When Nephi is told to go to the mountain, he clearly understands the request in terms of the sacred nature of the mountains, and like Moses, Nephi goes to the mountain to obtain the word of the Lord.
In this context it is again interesting that the command comes to Nephi and not to Lehi. It is probably that Nephi's physical ability to make a ship were greater than Lehi's but the reception of revelation is not dependent upon the ability to carry it out. Lehi received a revelation to send his sons to Jerusalem for the brass plates, and he could easily have received a revelation that Nephi should build a ship. He didn't. That revelation comes to Nephi directly. As has been increasingly the case in the last few chapters, the mantle of leadership is being lifted from Lehi, and placed on Nephi's shoulders. Lehi will continue to be the patriarch, and continue to command respect, but this is not Nephi's journey, and Nephi receives revelation directly for it.