Need help with chainsaw?

I have bought a used McCullough Timber Bear chainsaw and don't know if it should have regular gas or 2 stroke. I bought it at a going out of business sale at a small engine shop. It was marked as a fixed item that no one picked up. My son put gas in it, but it wont start so I'm thinking he should have used 2 stroke. If so, will it be ok to just drain the gas and put in the 2 stroke? THANK YOU!