One coulomb refers to the fundamental SI unit for charge. It refers to the charge in one Ampere (or current) that is passed for one second.
The amount of electron charge is 1.6*10-19 C.
For a 1 Coulomb charge, the number required for electrons will be:
Q = n*e
Q = 1 C, e = 1.6*10-19
n = 1 (1.6*10-19).
6.25*1018 number electrons