Hi
As already mentioned it should be in the handbook.
Can I ask why you need the wheel size? Are you replacing one wheel or all of them?
You will need more than wheel size if you are getting different alloys. (PCD, centre bore, ET, etc)
Tyre size will be on the tyre itself in a format like 185/55/R15.
Width of tyre/profile size/Radial(R) + wheel size in inches