If the old ECU isn't too dead to do it, you pull the as-built data off it and program into the replacement module.
If you can't do that, there are services that will sell you an ECU and when you provide your VIN, they can program it for you, for example:
1995 Ford Explorer Engine Control Computers. Car Computer Exchange offers ECM, TCM, and PCM auto computer control units for Chrysler, Dodge, Jeep, and Plymouth vehicles.
carcomputerexchange.com
However they seem to want your old ECU to activate the warranty on the new one, and might (??) want more money if you tell them you don't have the old one to do a core return. I suppose if they program it and send to you before you return the old one (that you don't have), then you might get away with sending them one that you pulled from a junkyard, or just your old one if you have it but it's dead. I don't really understand your intentions when you wrote " P.s: I don’t have the vehicle or the oldest ECU/ECM".