During the Crysis 3 Mission 3: The Root of All Evil, you can collect four Datapads.
Datapad no. 1
Once you reach the top of the dam, you will see two buildings. In the first one, see the screenshot below, hack the door, and you will find a datapad on the ammo crate.
Datapad no. 2 and no. 3
Near the end of the mission you will use the elevator to get inside the CELL System-X Harvesting Facility. Once you exit the elevator, turn left, and follow the path which leads to a computer terminal with a datapad. Proceed further and you will come across another computer terminal with datapad.
Datapad no. 4
Use the elevator to reach the top of the CELL System-X Harvesting Facility. When you exit the elevator turn left and you will see computer terminal with datapad no. 4.