WordPress htm plugins

Allows you to add a custom extension to your page URLs. This only affects pages created under the Pages menu and not your posts, category or tag URLs.

Appends .htm to the URL of PAGES when using permalinks

Converting an old HTML, PHP, or ASP site to WordPress? WP Page Extension will let you create pages inside of wordpress and give them any extension you …

Appends .htm to the URL of PAGES when using permalinks and swaps dashes with underscores