How to Hide Ni Purchase Order(PO) For WooCommerce Admin Menus

function plt_hide_ni_purchase_orderpo_for_woocommerce_menus() {
	//Hide "PO".
	remove_menu_page('niwoopo-dashboard');
	//Hide "PO → Dashboard".
	remove_submenu_page('niwoopo-dashboard', 'niwoopo-dashboard');
	//Hide "PO → Manage PO".
	remove_submenu_page('niwoopo-dashboard', 'niwoopo-manage-po');
	//Hide "PO → Stock Report".
	remove_submenu_page('niwoopo-dashboard', 'niwoopo-stock-report');
	//Hide "PO → Setting".
	remove_submenu_page('niwoopo-dashboard', 'niwoopo-setting');
}

add_action('admin_menu', 'plt_hide_ni_purchase_orderpo_for_woocommerce_menus', 100);

Where do I put this code?