Board Thread:Support Requests - Getting Started/@comment-27750212-20160216013203/@comment-5811199-20160217004756

You can request a database dump, which will back up the wiki into an xml format (which is what MediaWiki wikis use as backup). To make one, go to your wiki's Special:Statistics and scroll to the bottom, and click on the 'Request' button. Within a week (possibly within a day or two) you'll be able to download the wikitext of all pages.

If you want to just get several pages, Special:Export is also an option.

Do note that Wikia makes backups of wikis automatically as well.