To convert light-years to miles, you need to multiply the number of light-years by the number of miles in a light-year. One light-year is equal to approximately 5.88 x 10^12 miles.

So, 90000 light-years = 90000 x 5.88 x 10^12 miles

= 5.30 x 10^17 miles

Therefore, there are approximately 5.30 x 10^17 miles in 90000 light-years.