Exhaust part function assistance please.
 

Hello, some thief got under my truck and cut off a piece of my exhaust. Well, its actually a NV3500 and not a titan, but from what I've read its basically the same engine, exhaust, etc as the Titan so that's why I'm posting it here.
I think its a catalytic converter but the parts description is vague so I want to make sure its actually needed and is not just a resonance chamber or something. .
Nissan part 200109JJ0A. From what I can tell it's the passenger side catalytic converter, is this correct? Also, from the parts diagram, it looks like I have 4 cats, 1 attached to each header, then 1 more downstream of each header/cat, is that correct?

Thanks for any input or information.

https://cimg2.ibsrv.net/gimg/nissanf...107b821f7c.png