Praise be to Allah.
You must mean, is the Sunnah prayer before Zuhr two rak`ahs or four rak`ahs? Because the one rak`ah is odd-numbered, and there is no odd-numbered prayer apart from Maghrib, and the Witr prayer at night.
The answer is: it was narrated in some hadiths that the Sunnah prayer before Zuhr is with one taslim (i.e., it is two rak`ahs), as stated in the hadith of Ibn ‘Umar (narrated) in al-Sahihayn.
And in some other hadiths, it is narrated that it is two taslims (i.e., four rak`ahs), as stated in the hadith of `Aishah (may Allah be pleased with her), (narrated) in Sahih Muslim.
So one has the choice of doing two or four rak`ahs before Zuhr prayer . But some scholars suggested that if a person prays it at home it is better to pray four rak`ahs with two taslims, and if he prays them in the mosque, he should pray two rak`ahs with one taslim).
And Allah knows best.