28 yrs old smoked 1/2 pack a day for 12 yrs and quit 1 year ago what's the likelihood of me getting oral, throat and lung cancer?

Minimal risk. You are to be congratulated for quitting to smoke and staying off of them for rest of your life. I expect you to have no significant increase in risk of Cancer as long as you adopt a healthy lifestyle: No smoking, minimal or no alcohol use, eat healthy and keep your weight under control and exercise/walking daily to stay fit and avoid overeating and over weight.