Could you tell me what are chances of mouth cancer with no tabacoo at all or drinking?

Very low: Smoking, chewing tobacco and drinking alcohol can lead to oral cancer. A recent study showed that over 90% of oral cancers were associated with combining heavy smoking and heavy drinking while a virus is also suspected in oral cancer, the risk is very low in non drinkers and non smokers.

Extremely low: Extremely low. Drinking/smoking also causes many other cancers.