A light-year is the distance that light travels in one year in a vacuum, which is about 9.46 trillion kilometers.

Light-years are used because the distances between stars and galaxies are so enormous that kilometers would result in extremely large and unwieldy numbers.

5000 kilometers is an extremely small fraction of a light-year, making the conversion result very close to zero.

While technically convertible, 5000 kilometers is so small compared to a light-year that the result is effectively zero for practical astronomical purposes. The precise conversion is 0.0000 light-years.