QUESTION: How many "mL" in a "cc"
ANSWER: They are the same. They are measurements related to volume. The metric system has been coordinated so that length measurements are easily compared to volume measurements. The amount of volume of fluid that would fit in one cubic centimeter will be the same amount of volume of fluid that would fit in one milliliter.
You may interchange them. 3ml=3cc
QUESTION: What is a gauge?
ANSWER: The Needle size are available in a wide variety of diameters (thickness of the needle) and are described by the gauge. The "smaller" the Gauge number the "thicker" the needle. If you were injecting oil or thicker based products you would require a thicker needle for the fluid to pass, therefore a 28 or smaller would suffice. The same is true for thinner based medication, you would use a thinner needle (larger Gauge number)