Can anyone tell me the latest version of unity visual effect graph ? And how to install it?
I recommend using the latest stable version.
For visual effect graph to work you, need a Scriptable Render Pipeline, short SRP.
Universal Render Pipeline or High Definition Render Pipeline are prebuild SRPs.
You can install them in the package manager. Maybe take a look at this tutorial.
Then install visual effect graph also in the package manager, maybe you have to enable experimental packages. You can find a tutorial about installing visual effect graph here.
By the way, it would not be hard to google this by your own.