Wikipedia. The articles in English are little more than stubs, generally, but that's enough to give you a link to a map, and the full administrative pyramid. If you need to know more, follow the link to the French wikipedia and put the article in Google translate.
Châteauneuf or Châteauneuf-en-Auxois is a commune in the Côte-d'Or department in eastern France.
A search for "Châteauneuf" on Geneawiki yields 551 results! "Château-Neuf" (hyphenated) yields fewer results, but depending on your source, I don't know which one is correct.Châteauneuf 71740. Saône-et-Loire Bourgogne
As a general rule, I would recommend using Geneawiki's Régionalisme section with Google Translate on Chrome. It lists all the towns by department, including old towns that have since merged with their neighbor, additional details about each town (varies greatly), and links to departmental archives.
List of departments by region: https://fr.geneawiki.com/index.php/France
Maps by department (including arrondissements and cantons): https://fr.geneawiki.com/index.php/France_%28g%C3%A9n%C3%A9ralit%C3%A9s%29#Les_cartes_d%C3%A9partementales
(Sorry most of those resources are in French)