Example code recipe to modify the PMPro confirmation message.

my-pmpro-confirmation-message-example.php

<?php
/**
 * This recipe is an example of customizing the confirmation message displayed on
 * the PMPro confirmation page after checkout.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

function my_pmpro_confirmation_message( $message ) {
	$message = str_replace( 'Below are details about your membership account', 'Below are details about your enrollment', $message );
	return $message;
}
add_filter( 'pmpro_confirmation_message', 'my_pmpro_confirmation_message', 20, 1 );