Your answer would be 56m².
To find the surface area, you need to add up the total number of squares that can be seen on the outside of the solid.
First you have the front end which is made up of 4 squares, and there would be another one on the same side, so this comes to 8m².
The surface on top contains 12 squares, and this would also be the same on the bottom of the solid, so you get 24m².
The surface on the right-hand side also contains 12 squares and would be doubled on the other side, so this also comes to 24m².
Therefore your final answer is 8 + 24 + 24 = 56m².
I hope this helps!