There is no such thing as an 'equivalent HTML file' for an XML file. HTML is a form of XML, any browser can display XML as a normal HTML page, there's nothing special you need to do.
If you want to display it as html simply point your browser to the XML file just as it is (or make a link to it or whatever) and it will be displayed, tag by tag, item by item.
If you need special formatting, then you can simply take the info from the XML and manually format it with CSS into a normal HTML.
Note: you shouldn't change the extension since then the browser will try to read the XML as HTML, but it won't recognize the tags so you'll simply get a dump of the text inside tags.