XBee Shield V2.1, what modules are available?

I have 2 arduino uno’s with 2 Seed XBee Shields. I’m having a difficult time knowing what wireless modules are available and work with this combination. I need to know what all to buy as I’ve not done anything with XBee yet. Do I need the USB Explorer, and 2 of the same modules? Is it compatible with the Xbee 3 modules?

What do you need to do with it? Maybe I can help you.

I don’t need to do anything. I just have these 2 Seeed XBee Shields lying around that I have had for years and decided to used them for something, but I’m unsure what will work on them since V2 is retired.