What you have is a single phase unit. About 13,000 btuh. Not real large, enough to do a typical room. These units are designed to mount in a wall sleeve and are nothing more than glorified window units. A good quality window air conditioner will be better than a motel unit. The motel units are made for a very competetively priced market.
265 V Nominal rating is typical for a motor design to run on a 277 volt circuit. 277 volts is a single phase leg to ground of a 480 volt three phase (4 wire) system. It is used to keep circuit amperage down so wiring sizes can be smaller and thereby cheaper.
You cannot hook this directly to your panel. A nominal voltage of 240 will dip up to 10% below its nominal rating. Further more, a 240 volt system is across two phases of an electrical system. If your voltage goes to low, you will at the very least burn out the motors in the unit. You very well could short out the unit and start it on fire.
At the very least, you will need a boost transformer to up the voltage to a safe range and to isolate the unit from the electrical system. My guess is is by the time you buy a transformer of the size you need for this unit, you could purchase two good quality window units.
I would cash the unit in at the junk yard and not bother with it.