Assuming the raindrop was stationary relative to the vertical distance to the ground at the start:
D=0.5at where d is distance, a is acceleration and t is time
D is 300 meters
a is 9.8 meter/sec squared
Solve for t in seconds
t = 61.2 seconds
v=at where v is velocity
a is 9.8 meters per second squared
t is 61.2 seconds
solve for v
v = 600 meters per second.
If it had an initial vertical velocity (v0) at the start :
d= 0.5at+v0t
and
v=at+v0