If you didn't get any documents with your TT you will have to get the Manufacture's Name and the Model Number from each appliance in your trailer. Almost all of the manuals can be found on the manufacturer's website. Besides a pen and paper you might need a mirror and a flashlight. With the camera on the smartphones this a lot easier. Besides the ones I got with the TT, I have done this for my last 3 TT's I've owned and keep digital copies on my laptop. Another good way if you have a tablet that you can attach a USB thumb drive. Why the previous owner doesn't leave them with the trailer is beyond me. They will never need them again.
Refrigerator info will be on the inside of the door or door frame.
Water heater will be in the outside access panel.
Air conditioner most likely will have it in the access panel for the filter or you will have to remove the cover on the roof.
Furnace will be the hardest to get to but you will usually find it on a lable on the top side. You will have to remove the intake grill to get to it. This is a very good place to use your smartphone's camera.
The power distribution center (converter) will be another difficult one to get if the label is missing or un-readable from the access panel. The converters are most likely made by WFCO Electronics. The easiest will be to take a photo and compare to the ones on wfcoelectronics.com
. You can also post a pic on this forum with any info you have. Someone should be able to help you.
Another thing you should do with the distribution center is make a drawing with the breakers and fuses listing the sizes. Then turn off each breaker and make a note of what it turns off. The fuses will be fine just to have a list of the sizes and some spares. Changing these automotive type fuses will be easier if you have on of these pullers.