It came equipped with R12 Freon. R12 is extremely expensive as it is no longer produced. I suggest you have your A/C converted to operate on R134a. Any professional A/C shop can do this. You are asking this question so undoubtedly you have a leak, and the leak must be repaired before adding refrigerant. It is illegal to do otherwise.
R134a
134a is the refrigerant used by most vehicles made after 1995
Would have been built for R12, can be converted to R134a.
R134a
The green stuff
R134a
R134a
Consult the owners manual for that info.
5W-20 , according to the Owner Guide
It would use R134a refrigerant.
D O T ( 3 ) brake fluid
The 1998 Ford Taurus Owner Guide shows : Motorcraft MERCON - V , automatic transmission fluid For the AX4N and AX4S automatic transaxles