what is the relation between light year and kilimeter?
A light year is a unit of distance (not time!) equal to the speed of light in a vacuum times the duration of one Julian year--in other words, how far light could travel in a vacuum in a year, assuming no influence by gravitational or magnetic fields. It's used, mostly by laypeople, to discuss the differences in stars. (Professionals prefer the parsec.)
and a kilometer is the conventionally used measurement unit for expressing distances between geographical places in most of the world
kilometre symbol km is a unit of length in the metric system, equal to one thousand metres and is therefore exactly equal to the distance travelled by light in free space in 1⁄ 299,792.458 of a second