How many adapters do I need?

New to powerline ethernet.

I have two PCs in separate locations to connect to my one router via powerline. Do I need three or four netgear adapters to do this?

In other words, do the adapters only work in pairs, or can each interface with multiple adapters at the same time?

If multiple is possible, I can have one one adapter at each PC + one at the router (3 total) right?

Thanks!