Search engines now opt for XML sitemaps - not just a "list" of URL's
XML (Extensible Markup Language) has been chosen as the preferred system largely because it is "platform independent", and because it forces a set of rules on how data is represented.
You don't need to concern yourself with the technicalities of XML... You just need to know that, in order to satisfy search engines, your sitemaps need to be FORMATTED as XML files.
The first thing you need to do is "cuddle up" to the search engines.
Start with Google. Open an "account" with google, and register as a "webmaster". Load their Webmaster Dashboard facility, and verify your website as being part of your Google account. (There is a LOT of help at Google, so I won't repeat it here. Look at THIS LINK.
When you are set up with a webmaster account at google, and your site URL is VERIFIED as being associated with that account, do some learning on SITEMAPS.
When you are familiar with the above (both Google accounts and Sitemaps), then load THIS MODULE and run it