The obvious use of (external) interrupts here would be to detect the pulses from the anemometer and count these. Hint: use pin 2 or 3 on an Arduino (Uno etc.).You count these in the ten second period that has been specified in your school exercise. At the end of the ten seconds, you do a little maths to calculate the average wind speed in that 10 second period and, using Serial.print or some equivalent, write the value thus obtained to the PC.Your English, assuming you wrote the question, is not the problem here.
I´m really trying to solve this problem for school but i´m new at this
100 cpm is barely more than a pulse per second [. . . etc.]
Another one not paying attention in class. Looks like a job for Natural Selection.
Well at least the OP had the initiative to seek out a forum