An Einstein is defined as a mole of photons.

Therefore: microEinsteins per m² per second is identical to micromoles per m² per second.   1000 µE m^-2s^-1 ≡ 1000 µmol m^-2s^-1

Einsteins were interchangeably used along with µmol m^-2s^-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