Tell SearchWP to index WooCommerce Orders https://searchwp.com/docs/kb/searching-woocommerce-orders/

functions.php

<?php

/**
 * Tell SearchWP that it can index WooCommerce Orders.
 */
add_filter( 'searchwp_indexed_post_types', function( $post_types ) {
	if ( ! is_array( $post_types ) ) {
		$post_types = (array) $post_types;
	}

	if ( ! in_array( 'shop_order', $post_types ) ) {
		$post_types[] = 'shop_order';
	}

	return $post_types;
} );

/**
 * Tell SearchWP to index all WooCommerce Order post statuses.
 */
add_filter( 'searchwp_post_statuses', function( $post_statuses, $engine ) {
	if ( ! is_array( $post_statuses ) ) {
		$post_statuses = (array) $post_statuses;
	}
	
	return array_unique( array_merge( $post_statuses, array(
		'wc-pending',
		'wc-processing',
		'wc-on-hold',
		'wc-completed',
		'wc-cancelled',
		'wc-refunded',
		'wc-failed',
	) ) );
}, 10, 2 );