You have :
-------------
vf^2 - v0^2 = ( 2 ) ( -g ) ( yf - y0 )
vf^2 = vo^2 + ( 2 ) ( -g ) ( - 0.3 m )
vf^2 = ( 0.0 m/s )^2 + ( 2 ) ( - 9.807 m/s^2 ) (- 0.3 m )
vf^2 = 5.884 m^2 / s^2
vf = ( 5.884 m^2 / s^2 )^1/2
vf = - 2.43 m/s <-------------- [ minus sign since moving downward ]