Answer: 9 N/C.
Explanation: The direction of the electric field is from West to East.
We can use the equation for the acceleration of a charged particle in an electric field:
a = (q/m)E
where a is the acceleration of the particle, q is the charge on the particle, m is the mass of the particle, and E is the electric field.
Plugging in the given values, we have:
3 mm/s^2 = (-3 mC / 1 mg) * E
Simplifying and converting units, we get:
E = 9 N/C
Therefore, the direction and value of the electric field is from West to East with a magnitude of 9 N/C.