I need help writting a thesis statement for Melville's story "Bartleby the Scrivener, A Story of Wall Street."

A thesis statement for "Bartleby the Scrivener, A Tale of Wall Street" depends on the idea you have about the story, just like any other thesis statement (which is short for hypothesis statement: something to assert, examine, and prove). The point of a thesis statement is to tell your reader what you want to talk about in your essay; and what you want to talk about depends on what ideas you have about the story: what question does it make you think of; what disagreement with the story do you think of; what insight into the meaning of the story do you think of; etc.

For "Bartleby," you might have an insight into why Melville mentions the dead letter office at the end of the story. You might have an idea about whether Turkey and Ginger Nut and Nippers are respectfully treated in their jobs, jobs which, by the way, were standard jobs for many, many people in that era. You might have an idea about why the lawyer couldn't be assertive with Bartleby.

Until you state your idea, guidance on a thesis statement is limited. A thesis in general is a short summary statement that explains what you think. A thesis for one of the ideas I mention might be something like this: "Melville mentions the dead letter office at the end of the story to show that Bartleby's troubles started before his work for the lawyer and that he really has more freedom at the lawyer's office than at the dead letter office."