Customise the confirmation text on the confirmation page.

pmpro-customizations.php

<?php

/**
 * This recipe customises the confirmation text on the confirmation page.
 *
 * 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_gettext_confirmation_page( $output_text, $input_text, $domain ) {
	if ( 'paid-memberships-pro' !== $domain ) {
		return $output_text;
	}

	if ( $output_text === 'Thank you for your membership to %s. Your %s membership is now active.' ) {
		// replace text in quotes below with your desired text. Remember to always have the two %s placeholders
		$output_text = "LOREM IPSUM %s. DOLOR %s AMET";
	}

	if ( $output_text === 'Below are details about your membership account and a receipt for your initial membership invoice. A welcome email with a copy of your initial membership invoice has been sent to %s.' ) {
		// replace text in quotes below with your desired text. Remember to have the %s placeholder
		$output_text = "SIT AMET %s";
	}

	return $output_text;
}
add_filter( 'gettext', 'my_gettext_confirmation_page', 10, 3 );