If you're looking to cook something thoroughly in the microwave, you'll need to heat it to at least 165 degrees. But how long this will take depends on a few factors, including the wattage of your microwave and the size/shape of the food. So there's no one-size-fits-all answer to this question.
In general, however, it will take about 2-3 minutes to reach 165 degrees in a 1000 watt microwave. If your microwave is lower in wattage, it will take slightly longer; if it's higher in wattage, it will take less time. And keep in mind that larger, thicker pieces of food will also take longer to heat through than smaller, thinner ones.
So if you're looking to thoroughly cook something in the microwave, make sure it reaches an internal temperature of at least 165 degrees. This may take a few minutes depending on the factors mentioned above, but it's worth taking the time to ensure your food is cooked properly.