show custom filed inside billing details at admin code example
Example: Woocommerce Display field value on the admin order edit page [Custom Field Display 2]
/**
* Display field value on the admin order edit page..
*
* PHP Custom Feild Value
*
*
*/
add_action( 'woocommerce_admin_order_data_after_billing_address', 'my_custom_checkout_field_display_admin_order_meta', 10, 1 );
function my_custom_checkout_field_display_admin_order_meta($order){
echo '<p><strong>'.__('Store Location').':</strong> ' . get_post_meta( $order->id, 'My Field', true ) . '</p>';
}