Circular motion - change in radius and period

[Juliette]

An artificial satellite of the Earth rotates in a circular orbit of radius R (measured from the center of the Earth) with period T. By what factor must the radius of the orbit be changed for the satellite to rotate with period T/8

Answer is R/4

Hi everyone!
I don’t understand the formula to solve this question can someone solve?

[Ashwin]

You can use Keplers third law to find this

Law of periods should be used to solve this question