Take into account that the period is the inverse of the frequency. In this case, the frequency is 2000 rev/min, then, you have:
[tex]T=\frac{1}{f}=\frac{1}{2000}=0.0005\min [/tex]The period is 0.0005 minutes.
In seconds the answer results in:
0.0005 min = 0.0005*60 seconds = 0.03 seconds
The period is 0.03 seconds