I don't believe that particular statement actually appears anywhere in the Federalist Papers. They were basically "letters to the editor", written in 1788, after the Constitution (1787) but before the Constitutional Convention that ratified the Bill of Rights. They were essentially the political opinions of John Jay, James Madison and Alexander Hamilton, and were intended to garner votes for their positions at the Convention. The Federalist Papers are not law. They can be read here; a search on "militia" might be informative.