What did i do wrong...or at least did i do something wrong?

Conservation of energy... kinetic energy of the bullet before collision equals kinetic energy of the wood and the bullet after collision (neglecting energy lost due to heat of the impact, air resistance of the moving wood, the stiffness and m of the thing supporting the wood and uming the bullet is not travelling so fast that the bullet or the wood are vaporized in the collision) Check your units and you should get the right answer. good luck