Answer:
6 or 7, depending if you count the USS California, which was moored on the same side of Ford Island, but was in a different location.
The 6 other ships that were moored together as "Battleship Row" were:
USS Nevada (beached to prevent sinking)
USS Arizona (destroyed)
USS Tennesse (damaged), USS West Virginia (sunk upright, later repaired)
USS Maryland (damaged), USS Oklahoma (sunk - capsized, later raised but sank while under tow)
Tennessee / West Virginia and Maryland / Oklahoma were moored in pairs, with the second-named ship in each pair outboard (away from the island) and therefore vulnerable to torpedo hits.