Abbreviation for 35-millimeter as a description of film or tape. In this context, 35mm is one word, no hyphen. You do not have to spell out 35mm on first mention.

To describe a measurement of 35 millimeters, insert a space between 35 and mm.

Microsoft style

You can take your pictures on 35mm film and then convert them to a digital format.

Point A is 35 mm from Point B.

Use instead of 8.5 x 11-inch, 8 1/2 by 11-inch, or other ways of referring to the paper size.