Finding the magnitude of the eletric field of a uniformly charged rod.

Homework Statement

"A rod of 13.1 cm long is uniformly charged and has a total charge of -23.2 micro coulombs. Determine the magnitude of the electric field along the axis of the rod at a point 52.1575 cm from the center of the rod. The Coulomb constant is 8.98755e9 N M^2/C^2. Answer in units of N/C"
I'm lost on how to go about solving this. Ive tried just doing E=KQ/R^2 with R being 52.1575 cm and I tried E= KQ/(R^2+X^2)^2/3 with X= 52.1575 and R=13.1 but thats wrong to