themes-wordpress/xanadu/patterns/404.php

<?php
/**
 * Title: A 404 page
 * Slug: xanadu/404
 * Inserter: no
 */

declare( strict_types = 1 );
?>

<!-- wp:heading {"textAlign":"center","level":1,"fontSize":"x-large"} -->
<h1 class="wp-block-heading has-text-align-center has-x-large-font-size" id="oops-that-page-can-t-be-found"><?php echo esc_html__( 'Oops, this page cannot be found.', 'xanadu' ); ?></h1>
<!-- /wp:heading -->

<!-- wp:search {"label":"<?php esc_attr_e( 'Search', 'xanadu' ); ?>","showLabel":false,"width":518,"widthUnit":"px","buttonText":"<?php esc_attr_e( 'Search', 'xanadu' ); ?>","align":"center"} /-->