The diameter of Pluto is about 2376 km; therefore, due to the question being incomplete, I will suppose that the question states that the diameter of Pluto at its equator is 2.39x10^3 km.
Converting 2.39x10^3 km into standard form:

Therefore, the answer to part a) is 2390km.
b) Notice that there are 4 zeros between the digit 2 and the decimal point in 0.0000268; therefore,

The answer to part b) is 2.68x10^-5 meters