1994 Ford Aerostar drin plug

There is no drain plug. The fluid comes out when the trans pan is removed. Loosten one side, then remove the bolts from the other side slowly so it drops slowly and the fluid doesn't go everywhere.

As far as the capacity, when you remove the pan, you will loose around 4 quarts of ATF. Most of the fluid stays in the torque converter and throughout the rest of the trans.