Hi and welcome to the forum
What you have bought is an exhaust for a mk1 F which only have a pre cat sensor.
Your car will run without the post cat sensor but will through up a warning light.
Alternatively you could get a local engineering shop to weld a boss on or get the correct one for your car.
James
Home to black Alfa Romeo 159 3.2 V6 Q4 ,green MGF VVC and red MG Maestro T16.
MG - the friendly marque.