Pressure is given by P=F/A, where F is force and A is area. Neither are given in the question, but A is the area of the cube in contact with the table; this is the area of one face of the cube, so A=LL=0.050.05=0.0025 m2 (Side Note - Remember to convert to meters!).
Now we have A, we need F - this is given by F=ma, which is F=10*9.81=98.1 N.
Finally, P=F/A=98.1 N/0.0025 m2= 39240 Pa. (Side Note - 1 Pa=1 N/1 m2)