woocommerce new order do it use $order->set_status( code example

Example: woocommerce_order_status_completed

add_action( 'woocommerce_order_status_completed', 'update_frm_entry_after_wc_order_completed' );
function update_frm_entry_after_wc_order_completed( $order_id ) {
	$order = new WC_Order( $order_id );
	$items = $order->get_items();
	foreach ( $items as $item_id => $product ) {
		if ( isset( $product['formidable_form_data'] ) && is_numeric( $product['formidable_form_data'] ) ) {
			$entry_id = $product['formidable_form_data'];
			$entry = FrmEntry::getOne( $entry_id );

			if ( $entry && $entry->form_id == 25 ) {
				$field_id = 100;//Replace 100 with the field ID to update
				$new_value = 'Complete';
				FrmEntryMeta::update_entry_meta( $entry_id, $field_id, null, $new_value );
			}
		}
	}
}