change-wc-upsells-product-display.php

<?php
/*
 * Change upsells product display.
 *
 */
function wbcom_change_upsells_product_display( $args ) {
	$args['posts_per_page'] = 4; // 4 display 4 products.
	$args['columns']        = 2; // display product in 2 columns.
	$args['orderby']        = 'rand';
	$args['order']          = 'desc';
	return $args;
}
add_filter( 'woocommerce_upsell_display_args', 'wbcom_change_upsells_product_display', 20 );