Paste the code below to a HTML element. Adjust the url variables to your needs. Change the input $("input[name='var1']").val(urlname); and
$("input[name='var2']").val(urlstate); to your input var name. Next preview your form and find the item # of the div holding each var if you want it hidden. Mine were item4 and item5.

Here's what I put in the formbuilders Redirect to another url under Settings/Comfirm Options.

http://progrower.coffeecup.com/forms/passurlvariables2/?name=Mr.cool&state=Michigan

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script> <script>$(document).ready(function() {
function getQueryVariable(variable)
{
var query = window.location.search.substring(1);
var vars = query.split("&");
for (var i=0;i<vars.length;i++) {
var pair = vars[i].split("=");
if(pair[0] == variable){return pair[1];}
}
return(false);
}
var urlname = getQueryVariable("name")
var urlstate = getQueryVariable("state")
if(urlname != false && urlstate != false){
alert("Your name is " + urlname + " and your from " +urlstate);
$("input[name='var1']").val(urlname);
$("input[name='var2']").val(urlstate);


}else{
$("#item4").css("display","none");
$("#item5").css("display","none");
}
});</script>