Consider the kinematic equation
Δy = v0t + 1/2at2
Assuming the ball was dropped (v0 = 0), we can solve for time t such that
t = √(2Δy)/(a)
From this, you can see that the time on Earth, tE, and the time on Mars, tM, are related such that for the same drop distance Δy on each planet,
tE = √0.38 * tM
Thus, if tE is know, computing tM becomes trivial.