functions.php

remove_action( 'woocommerce_after_single_product_summary', 'woocommerce_upsell_display', 15 );
add_action( 'woocommerce_after_single_product_summary', 'woocommerce_output_upsells', 15 );

if ( ! function_exists( 'woocommerce_output_upsells' ) ) {
	function woocommerce_output_upsells() {
	    woocommerce_upsell_display( 3,3 ); // Display 3 products in rows of 3
	}
}