By default, Woocommerce does not allow the search by SKU And Many Store owners are looking for this functionality. We may need to add custom code to the functions.php file or simplay add the following free plugin.
In this tutorial, I will use search by sku for Woocommerce Plugin, You can download the plugin from here: https://wordpress.org/plugins/search-by-sku-for-woocommerce/
Now, if you will go to frontend again and search the product by sku it will search the product for you.
That is it. Thanks