In chemistry, as well as in many other fields, the abbreviation "atm" stands for "atmosphere." The unit atmosphere has a torr of 760.

It is the same time as you say

The SI unit for pressure is a Pascal but in this case the standard unit is the standard atmosphere (= 101325 Pa).

The Pascal; it is a derived unit, equivalent to 1 kgm-1s-2. Pascal

Atmospheres cannot be converter to milliliters. Atmospheres are a unit of pressure based on the Earth's atmosphere. Milliliters are a unit of volume, otherwise known as a cubic centimeter.