Helpful: Get all pro posts order by pro count

functions.php

<?php
/**
 * Shortcode for displaying all posts with pro, order by pro count
 */
function helpful_pro_shortcode() {

  global $wpdb;

  $table_name = $wpdb->prefix . 'helpful';

  /**
   * Select all pro posts
   */
  $sql = "SELECT DISTINCT post_id FROM $table_name WHERE pro = 1";

  $rows = $wpdb->get_results( $sql );

  $items = [];

  foreach ( $rows as $row ) :

    /**
     * Get pro count
     */
    $sql = "SELECT COUNT(*) FROM $table_name WHERE post_id = %d AND pro = 1";
    $sql = $wpdb->prepare( $sql, $row->post_id );

    $count = $wpdb->get_var( $sql );

    $items[] = [
      'post_id' => $row->post_id,
      'count'   => $count,
    ];

  endforeach;

  /**
   * Sort by count
   */
  usort( $items, 'sort_by_count' );


  $output = '<ul>';

  /**
   * Loop trough items and create a linked post list
   */
  foreach ( $items as $item ) :
    $output .= sprintf(
      '<li><a href="%1$s">%2$s</a> (%3$d)</li>',
      get_the_permalink( $item['post_id'] ),
      get_the_title( $item['post_id'] ),
      $item['count']
    );
  endforeach;

  $output .= '</ul>';

  return $output;
}

/**
 * Callable for usort (sort by count)
 */
function sort_by_count($a, $b) {
  return $b['count'] - $a['count'];
}

/**
 * Register shortcode
 */
add_shortcode( 'helpful_pro', 'helpful_pro_shortcode' );

/**
 * Usage: [helpful_pro] inside post content
 */