The answer is: hunger, thirst, and suffocation in the train car.
An external conflict is a struggle between a character and an opposing external force, such as an antagonist, who opposes the protagonist, or the forces or nature or society.
In "Night," the author Elie Wiesel is forced to endure against terrible conditions under the Nazis's rule, such as starvation, thirst, and the lack of air during the train ride to the concentration camp.
