Updating your plugin code to Woocommerce HPOS

1. Use CRUD

2. Declare compatibility

// declare compatibility on startup
use Automattic\WooCommerce\Utilities\FeaturesUtil;
add_action( 'before_woocommerce_init', function() {
	if ( class_exists( '\Automattic\WooCommerce\Utilities\FeaturesUtil' ) ) {
		FeaturesUtil::declare_compatibility( 'custom_order_tables', __FILE__, true );
	}
} );