The period of oscillation for an object hanging from an ideal spring is given by
T = 2 π√ (m ⁄ k), where m is our mass in kg and k is our spring constant.
The period of oscillation is independent of the object's velocity or position. The displacement x and velocity affects only the amplitude of oscillation, not the period.
So, since we know that the mass is 1.0kg and the spring constant is given to us as a, we can find our period of oscillation by plugging in
T = 2 π√ (1 ⁄ a) would be our period of oscillation.