What's the best extender for the Netgear Nighthawk r6400v2?

Or will any Netgear extender work with this? Sorry idk much about this stuff, but the wifi on the upstairs floor in my house is very spotty so I'm looking for an extender that'll solve this issue. I know this specific Nighthawk is a bit old, I believe it came out in 2015 or 2016, so hopefully there are extenders that work with it. Thanks in advance for any help.