Updating URLs is available for sites that have at least one Jira or Confluence product with a Standard, Premium, or Enterprise plan. You’re unable to update the URL if the site has only Jira Free and Confluence Free.

Please read our self help documentation on how to Update a product URL.

When you update a site’s URL, we store the previous URL in your site’s history and redirect all links to the new URL. This means that when your users visit old URLs (for example, links to Jira issues and Confluence pages), we redirect them to the new URL.

For migrating data between cloud sites please see this KB article.