The term used in the verse in revelation talking about hell being thrown into the lake of fire, is hádés, i.e. the underworld. Not some kind of a punishment hell like gehenna. I would guess the lake of fire is the gehenna.
Ghehenna is a dump where they burned trash (they burned bodies there to keep sickness down). Hades is a Greek myth term.
None of these have anything to do with a hell where sinners go....you crack me up!!