Where are the holding tanks on my 342? In the cabin under the sink or toilet or under the cockpit floor?

My waste tank is under the floor on the starboard side of the boat. The fresh water tank is on the port side. Also the pump and fitler is on the port side.

Frank

Imagine my surprise when I pulled up the STBD floor and there was nothing there. Turns out that my toilet is just a porta potti that you can pump out. Can I add a holding tank to this settup somehow? Maybe with a discharge pump.