what i need to upgrade my current rotor 280mm to S cooper specs. ( 294mm )

i need upgrade my calipers?

 

What year is your MC?

You might check around and see if-

For your year, the full MCS front caliper and rotor can be mounted to replace your stock MC caliper and rotor.

Get the JCW front brake kit.

Rear rotors and brakes are the same for MC and MCS

Another option is are you trying to get better stopping power or make the brakes look larger?

If only better braking then stick with the stock rotors and shop for better brake pads- something more performance minded. You may get a little more brake dust vs other aftermarket pads but less than a stock pad.