Change port 443 and 80

I could not understand exactly where I should add the port number in apache. I have a apache2.conf but dont know where to set the port number. Maybe at the end of “ServerName example.ddns.com” to “ServerName example.ddns.com:8443”?

In the apche2.conf there are referrals “ports.conf” and in that conf are port 80 and 443 set. Perhaps I need to change in ports.conf instead of apache2.conf?