Using Query Strings on Redirect page

I'm new to query strings, and am trying to get data to post to a redirect page after submit. On my site, I'm using gravity forms so users can purchase a service. The form redirects to PayPal and all is well. After confirmation of payment, they are redirected to a new page. I've passed the query string to the redirect page, but have absolutely no idea how to post data in Wordpress to show the query string. Call me a novice developer, I guess.

Could you give me the walk through, on how to populate data on a new page (not in a form), using the query string parameters outlined in the form settings, redirect page.

Thanks for the quick response David. A developer here just wrote a quick fix for future readers in javascript, which we pasted right in to Wordpress:

<script type="text/javascript">
function getParameterByName(name)
{
  name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
  var regexS = "[\\?&]" + name + "=([^&#]*)";
  var regex = new RegExp(regexS);
  var results = regex.exec(window.location.search);
  if(results == null)
    return "";
  else
    return decodeURIComponent(results[1].replace(/\+/g, " "));
}
jQuery(document).ready(function ($) {
   $('#order_number').html(getParameterByName('order_number'));
});
</script>
Order Number: <span id='order_number' />

Thanks for this, rcandela. Where exactly did you past the script to populate data in the redirected page?

Thanks for help.