A simple Google search of the motherboard will take you the ASUS site which also has your compatible RAM brands and speeds.
When you say 8GB of RAM, do you mean a single RAM of 8GB or a combination? I am asking because your motherboard says that it can have up to 16GB of RAM with 4 x DIMMs so the max capacity per DIMM is 4GB.
If you want a combination, then pick any from the list that you can find here:
https://www.asus.com/Motherboards/P5P43TD_PRO/HelpDesk_QVL/
go to the tab Memory/Device Support and then download the zip which has all the compatible RAMs for your motherboard.