As for free electrons inside a conductor, the most common material for a conductor of electric wires is copper and the electron density in 1m^3 is 8.5e28.
(the most common material for a conductor of electric wires; is; copper and the electron density in 1m^3) (copper; is a conductor of; electric wires)
the most common material for a conductor of electric wires copper
is is a conductor of
copper and the electron density in 1m^3
electric wires