Okay, this one is easy! To get the temperature in degrees Fahrenheit, you use the following conversion formula:
Fahrenheit = (Celsius) x 9/5 + 32 degrees Fahrenheit
So you take the 39 degrees Celsius, multiply that times nine, which is 351. Then, you divide that by five, which would be 70.2. The last step is to add 32 additional degrees to convert it over to a Fahrenheit temperature reading, so 70.2 + 32 = 102.2 degrees Fahrenheit.
Good gracious, have mercy! That child is burning up with fever, some one call the doctor!
I have enclosed a reference document that has other conversions for other temperature scales that are currently used in science as well. The United States is one of a few that still use the Fahrenheit scale. Most of the rest of the world uses the metric system scale, which bases the freezing point of water at 0 degrees and the boiling point at 100 degrees.