One acre of prime forage is supposedly enough for a colony. But, that's for a large industrial hive and under intensive agricultural conditions. If it were me I would start with 25 and observe from there. I'd also recommend, if possible, to have at least some of those be log hives. Even if your goal is production, these hives have a terrific survival rate (especially in cold climates) and you can use swarms from them to re-seed other hives during bad years. It's best to fill them with a swarm of local feral bees, if that's available.
Also, log hives can be smallish and have healthy, smaller hives. This means your land can support more of them down the line, and that means you'll have a healthy supply of swarms for repopulating your langstroths down the line.
Past about 2 miles it becomes relatively inefficient for bees to forage. This is because of calories burned, and wear and tear (and therefore shorter productive lifespans) of the workers. They can go further, as already said, but only if there is impetus to.