The number of standard cigarettes that are equal to a single Black and Mild depends on the standard of measurement used. For example, a regular-size Black and Mild contains upwards of 100 times more nicotine than a single cigarette.
A standard Black and Mild is a 4-6 inch cigar filled with pipe tobacco rolled in a tobacco leaf. Using nicotine levels as the comparison metric, one needs to smoke about 100 cigarettes to be exposed to the level of nicotine in one Black and Mild.
Black and Milds, however, are not intended for inhalation, but rather for cigar style smoking. The type of nicotine used in Black and Milds is easily absorbed through the walls of the mouth and doesn't need to be fully inhaled. Thus, using the intake of chemicals as a means for contrasting Black and Milds and cigarettes does not produce an accurate comparison.