Michelin Primacy 5 and Pirelli P Zero (PZ4) (225/45 R18 95Y XL) are available for G20 vehicles with BMW 18-inch all-round wheel fitment in the BMW 3 Series range at Tyres.co.uk. Check your registration, as other G20 wheel fitments can be staggered or can fit on run flat tyres.
The sidewall of the BMW 3 Series tyres has the information you need. For the factory specifications however, please refer to the tyre-pressure placard on the B-pillar of the driver's side. Fitments vary by generation, wheel choice and setups, so check the handbook or the registration.
For the BMW 3 Series, replacing all four tyres is not always required, but the same specification, manufacturer and tread pattern must be used across each axle. For BMW 3 Series xDrive variants, all four tyres must be the same and follow the approved staggered dimensions, with a maximum of a 2 mm difference in tread depth. It is recommended, when replacing two tyres, they be fitted to the rear axle.