A freeze plug is in the engine block itself; they look like small round caps pressed into the block. Get a Chilton or Haynes repair manual from a parts store.
There are only a couple of freeze plugs you can get to without removing suspension components or pulling the engine entirely (btw, any engine overhaul should include replacing the freeze plugs -- they're only a dollar or two each, so take the time to do it if the engine is already out for any reason), but the key is to make sure you get the correct size and then tap it into place using either a plug tool (the preferred method, as it will make sure you have seated the plugs evenly and to the correct depth) or by placing a socket just smaller than the plug inside the lip of the plug and using a socket extension and hammer to tap it into place. Take your time and buy a couple of extra ones in case you damage the first one when installing it -- since you'll lose most of your coolant when you remove the old plug (have a bucket handy!), you'll be without a car until you complete this repair and add more coolant.
The 1990 Ford Aerostar Maintenance Information manual says 21 gallons.
In a 1990 Ford Aerostar : You either have the 3.0 liter V6 engine or the 4.0 liter V6 engine from the factory ( each size of engine has 6 engine cylinders )
The distributor for a 3.0 liter in a 1990 Ford Aerostar rotates CLOCKWISE ( looking from the top ) The spark plug firing order is ( 1 - 4 - 2 - 5 - 3 - 6 ) The engine cylinder locations are numbered : 3 - 6 2 - 5 1 - 4 front of Ford Aerostar
See previous question of same nature.
Ford Aerostar was created in 1986.
Check the fuses first!
21 gal. probably, full it up and see.
1 - 4 - 2 - 5 - 3 - 6
Under tyhe dash driver side
3.0 Liter V6: freeze plug
Install a CD player in ford festiva wb model
A Haynes manual from Autozone and the like could have the answers you are looking for.