So a year ago it would not go forward or you have just tried it and it will not go forward. I would put it up on jack stands-ALL FOUR WHEELS- off the ground. Besure the earth is hard enough to be safe, dont want those stands to topple over while the wheels are turning. Inspect brakes on all four wheels including the parking brake cables ( highly possible that one or both are stuck holding the brake shoes tight to the drums),replace all worn, damaged,missing, or questionable parts. While it is up and easy to work on now would be the perfect time to check oil in front and rear differentials, transmission and transfer case. Once all of this is in dependable working order verify it is in 2WD and wheels are on truck, put vehicle in drive and see if the wheels will turn.
Providing that the rest of the drive train was in decent condition when last parked I would bet this will have it rolling again. Be sure to let us know what you find it always helps to hear "The rest of the story"