How can I find the PPF of an LED?
PPF is the number of photons (usually given in moles) that are emitted from a light source within the visible spectrum.  For a monochromatic LED, this is simple to calculate from the photon energy and the radiant flux given in the datasheet.  For a white LED, the calculation is more complex, but it can be estimated from the LED's spectrum and radiant flux. 

PPFD is the number of photons per area once you have installed the light into some device.  It depends on the PPF of the individual LEDs, how many there are, how closely spaced they are, the angle of emission, and the distance from which you measure.  It can be numerically solved using ray tracing software (provided you can get ray data for the LEDs), but more commonly it is measured once the device is installed.