Hello @rocketboy,
Thanks for writing in!
Because what you are trying to accomplish requires a template customization, we would highly to suggest that you use a child theme. This allows you to make code changes that won’t be overwritten when an X update is released.
Once you have your child theme active and ready, please follow the following steps below:
1] Using Notepad or TextEdit or Sublime Text or any text editor, please create a new file in your local machine.
2] Insert the following code into that new file
<?php
// =============================================================================
// VIEWS/GLOBAL/_CONTENT-404.PHP
// -----------------------------------------------------------------------------
// Output for the 404 page.
// =============================================================================
?>
<p class="center-text"><?php _e( 'The page you are looking for is no longer here, or never existed in the first place (bummer). You can try searching for what you are looking for using the form below. If that still doesn\'t provide the results you are looking for, you can always start over from the home page.', '__x__' ); ?></p>
<?php get_search_form(); ?>
You can change the text in the code above.
3] Save the file named as _content-404.php
4] Upload this file to your server in the child theme’s folder wp-content/themes/pro-child/framework/views/global/
You will need to create the folder path since it does not exist yet in your child theme.