My question is how can I change the ports that apache is listening to?
I was told to change it in a file called httpd.conf
But I can't find this file in terminal!
You'll find httpd.conf in the /etc directory.
An easy way of changing the ports is to use Onyx. I'm pretty sure this feature was in that. Remember though that you might have to open the new port in the firewall to allow it to work.