The working equation to be used for this is written below:
E = kQ/d²
where
E is the electric field
k is a constant equal to 8.99 x 10⁹ N m²/C²
Q is the charge
d is the distance
The charge for a proton is equal to 1.6021766208×10⁻¹⁹ C. Substituting the values:
E = (8.99 x 10⁹ N m²/C²)(1.6021766208×10⁻¹⁹ C)/(0.009 m)²
E = 1.778×10⁻⁵ N/C
