How to Hide WP Meta and Date remover Admin Menus

function plt_hide_wp_meta_and_date_remover_menus() {
	//Hide "Settings → WP Meta and Date Remover".
	remove_submenu_page('options-general.php', 'wp-meta-and-date-remover.php');
	//Hide "Settings → Affiliation".
	remove_submenu_page('options-general.php', 'wp-meta-and-date-remover.php-affiliation');
	//Hide "Settings → Contact Us".
	remove_submenu_page('options-general.php', 'wp-meta-and-date-remover.php-contact');
	//Hide "Settings → Upgrade".
	remove_submenu_page('options-general.php', 'wp-meta-and-date-remover.php-pricing');
}

add_action('admin_menu', 'plt_hide_wp_meta_and_date_remover_menus', 1000000000);

Where do I put this code?