Did you watch my 2048 game tutorial? It also merges tiles.
It seems you just have to do 2 searches. First move to the x,y of the same column, but the row of the destionation tile, and then from that tile left or right as a second step.
What you could also do is make a pathfinding behavior, and disable diagonals, and tweak a bit with the grid size? And then use the MoveTo behavior to move along the path.