i can't find the total DRY weight anywhere on it.can someone help ? thanx

Tow it to a scale and weight it.

I know that *I* don't.  I don't know anyone that does.  Sorry.

That information may have been on a LABEL on the frame that eventually
"disappeared" some time ago.  It has been, after all, outdoors for ~26-years.

Tow the camper to a scale.  It might be a few miles away, it might be 50.  
Doing this is worth the hassle.  It is NOT an unreasonable request of a seller.

Prior to picking-up my brand-new camper, I had the dealership fill the fresh
water tank and promise that the propane tanks were full.  This is known as
empty, "wet" weight.

After hitching-up to my new rig for the first time, I towed it out of the
parking lot and turned AWAY from home.  I towed the new trailer about 15 miles
to a big name truck stop and onto their scale.  I have the actual, certified
weight slips in a binder.  This might save me the hassle of a potential,
future buyer's request to take the camper to a scale - as I am recommending
YOU do.

One of these days, I'm going to RE-weigh the lashup, all packed-up and rolling
down the road enroute to camp.  I'm betting it will be an eye-opening figure.  
(I haul a LOT of stuff, now that I can.)

If the ACTUAL weight of the camper is of enough concern that it might make the
difference between using a "1/2-ton" or "3/4-ton" tow vehicle, you definitely
should have the trailer weighed.  If you already have a tow vehicle, you
should weight IT, with a full fuel tank, loaded for camping, with all usual
passengers IN the vehicle and any other luggage/stuff on the truck.

You need to know the tow rating of the intended tow vehicle.  That includes  
knowing the rear axle ratio and the engine displacement to make an informed
decision about the weight of anything you are - or might be - towing.

Your 1980 20ft Taurus travel trailer PROBABLY weighs somewhere in the
neighborhood (read: ESTIMATED) 3500-4000-lbs "wet" but empty.  Good luck!