Hi Nubiann,
Check on ‘wheelsize.com’. Enter your model etc. And it will display the wheel and tyre size for your car and also the Factory option sizes for your car. Stick to these sizes when buying your replacements and you should avoid any fitment issues and means you will avoid going outside the original ‘rolling circumference’ of the factory wheels.
Beware that 8.5j to 9.5j jump will reduce the clearance between the wheel/tyre and the suspension strut. You can compensate for this by fitting a wheel with a smaller ET (distance from hub face to wheel centre line) which will make the wheel protrude further, but this can make the tyre stick out past the wheel arch.
Basically, if you move outside of the factory option sizes listed for your car then you have to compensate by changing tyre size and/or wheel ET if you want to stay within factory limits.
I am guessing you should be looking for
255/35ZR21
8.5Jx21 ET30
5x112
Hope this helps. (For reference only of course)