How to Hide the "Pixel Manager" Admin Menu

function plt_hide_woocommerce_google_adwords_conversion_tracking_tag_menus() {
	//Hide the "Settings → Pixel Manager" menu.
	remove_submenu_page('options-general.php', 'wpm');
}

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

Where do I put this code?