Surely you can use. Vastu has nothing to do with No: 3. It does not deal with numbers. It deals with position or place of things.  According to Vastushantra, North-East position of the kitchen is the best place placing gas stove and cooking. You can cook with a gas stove  of any numbers.  In Numerology No: 3 represents Jupiter. Jupiter brings good luck and wealth. Therefore, no issues with 3 burner gas stove both from Vastu and Numerological point of view.