Answer: "..where ashes grow like wheat into ridges and hills and grotesque gardens."
Explanation: A simile is a figure of speech that consists in making a comparison between elements that aren't obviously related, this comparison is made using the words "like" and "as." In the given excerpt from "The Great Gatsby" by F. Scott Fitzgerald, we can see an example of a simile that compares the way ashes grow with ridges and hills ("a fantastic farm where ashes grow like wheat into ridges and hills and grotesque gardens").