The force that an object feels in an electric field is the magnitude of the electric field E times the charge on the object Q.
We know that the magnitude of the charge of an electron is 1.6 x 10^{-19} C
F = E x Q
E = F / Q
E = (3.5 x 10^{-16} N) / (1.6 x 10^{-19} C)
E = 2.19 x 10^3 N/C
The magnitude of the electric field at the location of the electron is 2.19 x 10^3 N/C
