Convert from femtometer to fathom [ancient]

Unit Definition (femtometer)
a metric unit of length equal to one quadrillionth of a meter.

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.