Firstly convert your number to hexadecimal with leading zeros and then format it by adding dashes.
Example
You can try to run the following code to format hexadecimal number −
<!DOCTYPE html>
<html>
<body>
<script>
var num = 32122;
var myHex = ("000000000000000" + num.toString(16)).substr(-16);
var resHex = myHex.substr(0, 8)+'-'+myHex.substr(8,4)+'-'+myHex.substr(12,4);
document.write(resHex);
</script>
</body>
</html>Output
00000000-0000-7d7a