Exhaust Confusion Options

[Villager]

Hi there, this is my first post.

I have a 1997 (R reg) Corolla. The exhaust has been blowing and when I jacked it up I saw that the long pipe was heavily corroded in the middle.

I didn't have the best light but it looked like the back box, middle pipe (whatever you call it) and cat were all one piece. I found some info that says that they were originally two-piece, and are now supplied in four separate sections, but I'm struggling to figure out which parts I need.

Can anyone shed any light on this?
Where is the cheapest place to get these parts?