If you have a citation that gives a specific NARA microfilm publication number, like M2061 or T252, it is easy to find the film information on the NARA site. On the Microfilm page type in the microfilm publication number with NO SPACES in either of the search boxes.
One record was found for this publication number
By clicking on the title, which is highlighted above, you will get detailed information including the number of rolls, the digital availability and the viewing locations.