A footcandle is the amount of light a candle generates when it is 1 foot away. For example, if you have a lightbulb which is said to produce 50 footcandles of light, it means that it produces the same amount of light that 50 candles would emit from 1 foot away. As you move farther from the light, the light gets dimmer and the number of footcandles decreases.
The lumen, on the other hand, is the total amount of light that is being given off by the source. This number doesn't change with distance because the measurement pertains only to the source of light, not the perspective of another object or person.
There isn't a direct conversion simply for the footcandle to the lumen because they are two different physical properties. There is no real comparison for these two, either, but there is another conversion available. As you will find with online unit converters, footcandles are converted into lumens per square foot, which is actually a simple conversion.
One foot candle is equal to approximately 1 lumen per square foot. So if you have 10 footcandles, you have 10 lumens per square foot. This is an approximation, though.
