Hey there! I'm happy to help!
All of the sides of a square are the same. Therefore, to find the area, you multiply the side by itself. Multiplying a number by itself is conveniently called squaring.
Doing this backwards is called finding the square root. If you have an area of 64, you square root it, showing you that the sides are 8.
Therefore, the side length here is √94.
If we put √94 into the calculator, we see that it is 9.895359715.....
That number never ends and it goes on in no particular order, so it cannot be written as a fraction of two integers and therefore is not a rational number.
Have a wonderful day! :D