Before you start looking for an engine, pull the plugs and try turning the engine by hand with a breaker bar and socket on the crankshaft pulley nut. If it won't turn, you might even try squirting some WD40 in the plug holes and letting it sit for a day or so and then trying again. If it turns, put in a couple of new batteries and try and start it. The fuel in the tank will most likely be bad so you may want to rig a small portable tank with fresh fuel.
Good luck.
Good luck.