This is a dimensional analysis problem.
To solve it you need to convert the energy (2.2 x 1024 J) into the rise of sea levels (in meters).
some useful info from which we can derive the conversion factors
It takes 334 J to melt 1g of ice
The mass of 1 m3 of water is 1000 kg = 1 x 106 g
Now let us set up our calculation. We need to be paying attention to the units
2.2 x 1024 J x ( 1g / 334 J ) x ( 1 m3 / 106 g ) / ( 0.7 x 5.1 x 1014 m2 ) = 18.45 m
Rounding the result to two significant figures we get 18 m