I went to the muffler shop and the guy told me that I had 4 catalytic converter's on my 1995 Grand Marquis. I would like to know if this is true.

I believe there's one two-part converter assembly. Check AutoZone part no. 652044.

Two converters, two resonance chambers and, if it's equipped with dual exhaust, you have two mufflers.
Single exhaust has only one muffler.