What you're looking for is how to set up something known as a name-based virtual host. This is a feature where a webserver examines the HTTP/1.1 HOST header supplied in a web browser's request and uses this to determine what website is being requested.
None of these websites would need their own unique ports configured (unless special circumstances arise): they can all share port 80.
While it would be possible for someone who knows
IIS better than me to guide you through this process, I think it would be best to steer you toward seeking some self-education on the topic of web hosting. Name-based virtual hosts are considered fairly basic knowledge in professional hosting environments, and you are going to run into many problems trying to set up working configurations if you have not been exposed to the names of concepts like this one. It's hard to search for help on Google otherwise, nevermind this website. :)
We're here to help you with technical problems that you run into along the way, but it'll be a very slow and inefficient process to help you every time something like this pops up.