My doctor has prescribed me salicylic acid gel cleanser and differin (adapalene) for my acne marks, do you think it's effective for acne marks?

Depends: This depends on the severity of the scars/marks. It is a good regimen for preventing new acne scars, but ones that are already present pose a different problem. If you have deep pits and scars from previous cystic lesions, even the salicylic acid may not be enough to remove these. You may want to work with a dermatologist or even a plastic surgeon if you have significant scarring.