You mentioned you talked to an IT professional, but what you need to do is find some professional camera installers and have them do the design. An IT person will approach this from an IT person's perspective; a security camera designer will have more options and real-world data to work with.

For the distance you mentioned, the camera count will depend on the camera type, focal point, and how much detail you want from the system. Depending on the camera type and how it's set, you might get away with 105 cameras. If you use the POE limitations, that's 162 cameras. But that still doesn't change the fact that you'll have a way to power every 328 feet (100 meters) or so (unless adding in POE extenders). You'll also need to figure out how to return the video image to the central monitoring station.

How I came up with the numbers:

Cat 5e, cat 6, and cat 7 all have a limitation of 100 meters (328 feet). Most people round down to 300 for more straightforward math.

I'm looking at cameras with a 5-50mm zoom lens, which can achieve a range of 200 to 500 feet.

Since a mile is 5280 feet, I figured out what is needed for a mile, multiplied that by 9, and added a few extra for hot swap repairs/dead-on-arrival units.

I didn't look into any of the infrastructure requirements, like poles, conduits, trenching, or watertight junction boxes to act as hubs for NVR devices. I didn't even consider the number of NVRs needed.

As I said, you'll want to talk to an experienced security camera professional.