To make the origin have a electric field of 0, we first need to find the electric field at the point right now.
E1 = (10.8x10^-9)(9x10^9)/(8.66x10^-2)^2 = 12960 V/m
E2 = (2.81x10^-9)(9x10^9)/(5.44x10^-2)^2 = 8548 V/m
Now to find E total
E1+2 = sqrt(E1^2 + E2^2) = 15524.5 V/m
So if we want to make the origin have an E-field of 0 V/m, we will need to make an E-field equal and opposite to the current one
E3 = 15524.5 = (14.31x10^-9)(9x10^9)/(d)^2
d = 0.00829 meters = .8 cm