We have the following formula for the surface area of a regular pyramid:

where A is the area of the base, P is the perimeter of the base and s is the slant height.
In this case, we have a squared base, then, we have the following:

then, using the formula above, we get:
![S=49+(1)/(2)(28)(12)=49+(1)/(2)(336)=49+168=217\operatorname{cm}^2]()
therefore, the surface area is 217cm^2