How was the lewis and clark expedition able to get horses for crossing the mountains from the shoshones?

Lewis and Clark could cross the mountains been helped by the Shoshones' Indians. These Indians had no knives or hatchets, all their wood was split with a wedge of elkhorn and a mallet of stone, their guns were really antiquated. the captains took advantage of this and decided interchange their knives and guns for the Shoshones' best horses.

Once the interchanged was performed. They pointed out an old man that knew the rivers and the mountains, to be the guide.

The horses were brought, and with forty horses and three colts, the captains Lewis and Clark and their devoted followers struggled on to cross the mountain.

bless you your highness