Compatibility snippet to use the WooCommerce Shipment Tracking Plugin with WooCommerce Basic Order Numbers by OpenTools. WooCommerce Shipment Tracking Pro Plugin - https://www.pluginhive.com/product/woocommerce-shipment-tracking-pro/

functions.php

/**
 * Snippet to resolve Shipment Tracking Pro compatibility issue with WooCommerce Basic Ordernumbers by OpenTools.
 * Created at : 16 April 2018
 * Updated at : 16 April 2018
 * PluginHive Plugins : https://www.pluginhive.com/product-category/woocommerce-plugin/
 * Gist Link : https://gist.github.com/xadapter/611aee58bbc2322fcf6a62271c80c6d9
 */
add_filter( 'xa_tracking_importer_order_id', 'xa_get_order_id_from_order_number' );

if( ! function_exists('xa_get_order_id_from_order_number') ) {
	function xa_get_order_id_from_order_number($ordernumber) {

		$ordernumber_meta = '_oton_number_';
		global $wpdb;
		$meta = $wpdb->get_results("SELECT * FROM `".$wpdb->postmeta."` WHERE meta_key='".esc_sql($ordernumber_meta.'ordernumber')."' AND meta_value='".esc_sql($ordernumber)."'");
		if (is_array($meta) && !empty($meta) && isset($meta[0])) {
			$meta = $meta[0];
		}
		if (is_object($meta)) {
			return $meta->post_id;
		} else {
			return $ordernumber;
		}
	}
}