How many calories can I burn walking 2,000 steps per half hour?

The calories you burn depend on a number of factors including you body weight and level of fitness.  Based on an average stride length, there are approximately 2000 steps in a mile.  So, that would put you at a pace of about 2 miles per hour.  A 150 lb person would burn about 68 - 95 calories in a half hour of walking at that pace depending on which estimation you use.  To get a more accurate calorie count, I would recommend getting a device like the Exerspy or a heart rate monitor to keep track of your calories burned.