An Einstein is defined as a mole of photons.
Therefore: µEinsteins per m2 per second is identical to µmoles per m2 per second. 1000 µE m-2 s-1 ≡ 1000 µmol m-2 s-1
µEinsteins were interchangeably used along with µmol m-2 s-1 in the 60’s and 70’s, but the Einstein is not a unit in the SI (International System) of units, so using moles is preferred.
For more information see:
Units, Symbols, and Terminology for Plant Physiology A Reference for Presentation of Research Results in the Plant Sciences Edited by Frank B. Salisbury Oxford University Press, 1996