As per Kepler's law we know that
[tex]\frac{T_1^2}{T_2^2} = \frac{R_1^3}{R_2^3}[/tex]
as we know that for earth the time period is 1 year and its distance is 1 AU
now from above formula we can say
let the time period of Neptune is T and its distance is given as R = 30.06 AU
now we will have
[tex]\frac{1^2}{T^2} = \frac{1^3}{30.06^3}[/tex]
by rearranging the above equation we have
[tex]T^2 = (30.06)^3[/tex]
[tex]T = 164.8 years[/tex]
so it will have time period of 164.8 years