1984 crown vic with new battery will not start. its getting fire but will not turnover.

I have a 1984 Crown Victoria and I'm trying to find the OBD plug in, If you know if it has a plug let me know where it is, thanks!

IF THE PROBLEM IS NOT THE FUEL PUMP, FUEL RELAY, FUEL PRESSURE, AND OR FUSE WAT ELSE COULD B THE PROBLEM

Crown Victorias that year came with two engine options.
The regular Crown Vic had a 302 cubic inch engine.
The Police version had a 351W.
The 351W is a much better, stronger engine.
The easiest way to tell at a glance is to see if you can access the bottom thermostat housing bolt with a socket. If you can it's a 351W. If you can only get a wrench on that bolt, then it's a 302.

I would check the plugs around and on the engine. Also check to see if the inertia switch in the trunk was tripped, that cuts off power to the fuel pump in an accident.

I would visually check for spark at the plugs, to make sure spark is getting to the plugs. If spark everywhere, use a gage and check proper fuel pressure and fuel injector pulse.
How long since a tune-up? Any applicable trouble codes?

buy a cheap volt meter check voltage on both sides of the starter seleniod on the fenderwell if you have 12 volts on both sides while cranking test voltage at starter if you have 12 volts at starter with fully charged battery and it doesnt start you will need a starter it also sounds like you might need an alternator once you can get it started

ignition switch or starter relay or a wiring problem

It should be listed on the driver's door post. The correct size for your car is 215/70-15

The most commonly used V-8 used in the 1984 Crown Victoria is the 5.0 liter /302 cubic inch engine.

Check the starter solenoid. Usually mounted on a fender well. Find by following the + battery cable.