Recommend Tire Pressure

Donn is correct. No one knows how much pressure need. You determine that from the max pressure on the sidewall, and the weight you carry. There may be a time where the max is too much, and that is determined by visual treadwear. If you run max pressure, and the center tread wear is not excessive, then you can't do any better.
There may come a day (maybe on a cargo trailer) when you mite need to run more than max pressure, such as in an overload situation. Running over max pressure is much better than failure from an over heated tire.

Yes.

Well I did weigh the trailer empty and that is the 8180 pounds. The weight for water, food, clothing I am estimating at 600 pounds.
Point well taken on the "inflate to max" suggestion. My only concern with that is that pressure when hot would build above the maximum. You make a point that the recommended max is COLD pressure so a safety factor for hot running is built in?

Agree with donn0128. Have run max sidewall pressure on last 6 trailers including current one and have never had a problem. I think people totally over complicate this tire pressure issue. It is really not that hard. My opinion.

What a waste of time! Inflate the tires to max listed on the tire sidewall. You may not need that number, but at least you aren guaranteed the tires will A, run cool, and B, will be able to carry the max load as stated on the tires. Otherwise, you would be required to get each corner weight and adjust the COLD tire pressure before each trip. In all my years I have always ran my tires at max pressure. I have never ever had a tire wear out because of over inflation.

Is there NOT a label somewhere on the unit that lists the tire pressures ??
I think there should be. Also owners manual or contact a dealer or the mfg.

In addition to listing the 80 PSI on the sidewall, it should also list the max. weight load at that pressure. If that is less than 2200 but near, then 80 is probably right.

You really need to get it weighed to get the proper inflation for the weight