A lumen is a unit of light output from a source. It's measured in foot candles: one lumen of light is equal to one foot candle of light falling on a 1-foot-square area 1 foot away. Candle power is measured at the light source (right next to the bulb), and it's how much light the bulb (or other light source) produces. Candle power tells us how much light a source emits, while lumen refers to how much of that light we want to fall on an area some distance away. Although there's no direct conversion between candle power and lumens, you can get a good approximation.
Find out the lumens for the light source. Manufacturers generally measure light sources in lumens and put this information on the product (either on the box, or on the unit itself).
Measure the lumens with a light meter, if you cannot find the lumens on the box or product.
Divide the lumens by 0.07958. For example, 100 lumens / 0.07958 = 1257 candlepower.