How to Hide PlainInventory Admin Menus

function plt_hide_z_inventory_manager_menus() {
	//Hide "PlainInventory".
	remove_menu_page('z-inventory-manager3');
	//Hide "PlainInventory → Inventory".
	remove_submenu_page('z-inventory-manager3', 'http://127.0.0.1/wp-admin/admin.php?page=z-inventory-manager3&zi3a=items');
	//Hide "PlainInventory → Transactions".
	remove_submenu_page('z-inventory-manager3', 'http://127.0.0.1/wp-admin/admin.php?page=z-inventory-manager3&zi3a=transactions');
	//Hide "PlainInventory → Contacts".
	remove_submenu_page('z-inventory-manager3', 'http://127.0.0.1/wp-admin/admin.php?page=z-inventory-manager3&zi3a=contacts');
	//Hide "PlainInventory → Users".
	remove_submenu_page('z-inventory-manager3', 'http://127.0.0.1/wp-admin/admin.php?page=z-inventory-manager3&zi3a=admin%2Fusers');
	//Hide "PlainInventory → Settings".
	remove_submenu_page('z-inventory-manager3', 'http://127.0.0.1/wp-admin/admin.php?page=z-inventory-manager3&zi3a=admin%2Fsettings');
	//Hide "PlainInventory → Premium add-ons".
	remove_submenu_page('z-inventory-manager3', 'http://127.0.0.1/wp-admin/admin.php?page=z-inventory-manager3&zi3a=promo');
	//Hide "PlainInventory → Upgrade".
	remove_submenu_page('z-inventory-manager3', 'z-inventory-manager3-pricing');
}

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

Where do I put this code?