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Terminal Velocity and The Millikan Oil Drop Experiment

I have been trouble finding the terminal velocity of the drops of oil in Millikan's experiment.
The equation it gives me for the mass is:
http://i.gyazo.com/1a1154e3dec32464b514c7b8f898766d.png
However, I need to find the terminal velocity before finding the mass. It gives me the time only, but how to I incorporate time into the terminal velocity equation?
Terminal Velocity equation: v = 2 (r^2)(p)(g) /9n
where
v = terminal velocity (m/s)
r = radius of the drop (I think this is 0.01m)
p = density of oil = 923 kg/m^3
g = 9.81 m/s^2. My friend said this should be the universal gravitation constant but I don't know if he is trolling me!
n = viscosity of air = 1.83 x 10^-5 kg/m/s

The time for the first droplet is 18.5 seconds to drop 0.01m. How do I calculate terminal velocity with time?

Thanks in advance