Pulling down hint from the Windows menu (or pressing command-I) will bring up a dialog box telling how many moves are possible. If there are two or more possible moves, then one of the tiles that can be moved will be shown in the dialog. Note that this hint is not necessarily the best move you could make; Mombasa just chooses randomly from among the possible moves.
By the way, one legal move is counted if a removeable tile has at least one removable match on the board, so it will only count as 1 legal move if 2 of a design, or 3, or 4 can be removed.
