1)
To where will they take the rocks?
1.
Rashi: They took them to Har Eival, like it says in the Torah (Devarim 27:4). They built a Mizbe'ach, wrote the Torah on the rocks, offered Olos and Shelamim, ate and drank, scraped [the plaster] off the rocks and came to Gilgal.
2.
Malbim: They will take them with them to the place where they will lodge at night.
2)
From where exactly will they take the rocks?
1.
Malbim: "Mi'Zeh"
