Hey there! I'm happy to help!
If you have the area of a square and want to find a length, you simply square root the area!
√3820≈61.80614856.....
Therefore, the length of one side is in between 61 and 62 ft. You could also approximate this by seeing that 3820 is near to 3600 which is 60². Then you count up!
61²=3721
62²=3844
3820 is in between these two, so the square root of it has to be in between 61 and 62.
Have a wonderful day! :D