Add a custom column to the Memberships > Members admin page for a user field added via Register Helper using the PMPro hook method.

my_pmpro_memberslist_extra_cols.php

<?php
/**
 * Add a custom column to the Memberships > Members admin page for a user field
 * added via Register Helper using the PMPro hook method.
 * 
 * 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/
 */

// Add 'Company' Column to Members List Header.
function my_pmpro_memberslist_extra_cols_header( $theusers ) { ?>
	<th><?php _e('Company', 'pmpro');?></th>
	<?php
}
add_action( 'pmpro_memberslist_extra_cols_header', 'my_pmpro_memberslist_extra_cols_header' );

// Add 'Company' Column to Members List Rows.
function my_pmpro_memberslist_extra_cols_body( $theuser ) { ?>
	<td>
		<?php 
			if ( ! empty( $theuser->company ) ) {
				echo $theuser->company;
			}
		?>
	</td>
	<?php
}
add_action( 'pmpro_memberslist_extra_cols_body', 'my_pmpro_memberslist_extra_cols_body' );