Convert from light year to fathom [ancient]

Unit Definition (light year)
The distance that light, moving at a constant speed of 300,000 km/s, travels in one year. One light year is about 10 trillion kilometers.

Unit Definition (fathom [ancient])
A fathom is a unit of measure equal to 2 yards or 6 feet, or 1.8288 metres. The name of the unit derives from the Old English word fæthm meaning 'outstretched arms' which was the original definition of the unit's measure.