How to Hide 404s Admin Menus

function plt_hide_404s_menus() {
	//Hide "404s".
	remove_menu_page('edit.php?post_type=404s');
	//Hide "404s → All 404s".
	remove_submenu_page('edit.php?post_type=404s', 'edit.php?post_type=404s');
	//Hide "404s → Add New".
	remove_submenu_page('edit.php?post_type=404s', 'post-new.php?post_type=404s');
	//Hide "404s → 404s".
	remove_submenu_page('edit.php?post_type=404s', '404s');
	//Hide "404s → Settings".
	remove_submenu_page('edit.php?post_type=404s', '404settings');
	//Hide "404s → Export 404s".
	remove_submenu_page('edit.php?post_type=404s', 'panel404sExport');
}

add_action('admin_menu', 'plt_hide_404s_menus', 11);

Where do I put this code?