Where download playstation 2 cores ?
Here cores don’t exist http://buildbot.libretro.com/nightly/windows/x86_64/latest/
Also don’t exist in online updater. Maybe I’m blind.
There is none yet.
You’re best bet for now would be to go with the standalone PCSX2 v4.0. Sadly, no PS2 core has been made yet.
It’s the same with Gamecube/Wii. They just barely got that era started with Dreamcast implementation with Reicast so I’d give it some time.
(Although I wouldn’t hold out for XBOX any time soon 
)