If this messure is in inches, multiply with 25.4 and you get millimeter. Focal ratio is the ratio between the apertude and the focal length of your telescope. If you want to calculate the values with barlow-lens, multiply the focal ratio with the magnification of the barlow. Focal length of eyepiece is usually marked on the eyepiece. Comes always in millimeter.
Apparent field is marked in degrees.
The manufacturer of the eyepiece give the apparent field in their technical data. Camera gives you the oportunity to choose the camera you want. Focal length is the distance from where the light is first bent till it meets in focus. Magnification is by many considered as the most important thing at the telescope. The magnification is rather insignificant, but is convenient for comparing preformance of different telescopes.