I can’t tell you what page the story is on in your textbook, but I can tell you that your teacher will not care as long as you use the actual story in your essay. You just need to provide a citation of the story, the same way you would cite your textbook. The full text of the story is available online.
You can use this page to find quotations and page numbers. Since it is not clear what you essay is on, there are some quotations that can be useful. You can print the story or print preview to find the page number.
"I wanted the ideal animal to hunt," explained the general. "So I said, `What are the attributes of an ideal quarry?' And the answer was, of course, `It must have courage, cunning, and, above all, it must be able to reason."' (p. 7)
This quote demonstrates that Zaroff was interested in hunting something more interesting than animals. This is why he began hunting human beings instead.