I recently decided to free up the PC solely for work and bought a PS3 for gaming. I was wondering if I can transfer my PC MW3 saves and continue to play on the PS3? Or will I have to start from scratch?
Short and simple: You'll have to start from scratch.
Yes, you would have to start from scratch. This would also be breaching the terms and agreements of at least Sony Computer Entertainment of America's terms. I wouldn't try it.