I'm fairly sure that you can make use of the formula:
h=v_{i}t+\frac{1}{2}at^2
And do it as you started:
2.55(1.85)^3=v_{i}t+\frac{1}{2}at^2
And then initial velocity is zero, and a is the gravitational constant g=9.8m/s^2:
2.55(1.85)^3=0t+\frac{1}{2}9.8t^2
And then solve for t.