Permutation and combination

Since the number of  fingers of right hand is not mentioned So we are assuming all the five fingers (including thumb) can be considered

The first ring can be worn in any of the 5 fingers.

So there are 5 ways of wearing it.

Similarly each one of the other rings can be worn in 5 ways.

Hence, the required number of ways = 5 x 5x 5 x 5 x 5x 5 x 5 x 5 = 5⁸