Lets take velocity of object at the window's starting level as "v"

time taken by object to cross the window= 1/6 second

So using Second equation of motion

v*(1/6) + (9.8*(1/6)^2)/2 = 3

This gives v

Now Let us take the distance of origin to window = h

Initial velocity is 0

Velocity after traveling h distance is given by

Using Third equation of motion

v^2 -0^2 = 2*9.8*h

Thus you get h after putting v