To find the length of side \( AD \) in a parallelogram, we would typically use information about the lengths of other sides or angles, or coordinate points for vertices if provided. However, since I do not have specific lengths, diagrams, or additional context, I can only guide you on how to calculate it.
In a parallelogram, opposite sides are equal in length. Therefore, if you know the length of side \( BC \) (which is opposite to side \( AD \)), then:
\[ AD = BC \]
If the parallelogram has angles or coordinates given, you could also use the Law of Cosines or the distance formula, respectively. If you could provide these specific details, I'd be happy to assist further!