Convert from palm [US, Roman major] to attometer

Unit Definition (palm [US, Roman major])
A palm, when used as a unit of length, is usually four digits or three inches, i.e. 7.62 cm (for the international inch). The width of an adult human male palm is indeed about 10 centimetres.In English this unit has mostly fallen out of use, as do others based on the human arm: digit (¼ palm), finger (7/24 palm), hand (4/3 palms), shaftment (2 palms), span (3 palms), cubit (6 palms) and ell (15 palms).

Unit Definition (attometer)
An Attometer (or attometre) is equal to one quintillionth of a meter, or sometimes denoted as 10e-18 meters. The origin of the prefix is atten, the word for 18 in Danish and Norwegian.