Where can I find in the Holy Qur'an the verse that states stoning (stoning a married man/woman if they commit adultery (Zina)?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

The verse that states the ruling of stoning was revealed to the Prophet and then abrogated as a text in the Quran, but its ruling has been still valid and effective.

‘Umar Ibn al-Khattab narrated: “Allah, The Exalted, has sent Muhammad with the truth and He has sent down the Quran on him, and among the revealed verses was the verse of stoning. I recited it, retained it to my memory and comprehended it. The Prophet stoned adulterers to death and we did the same after him. So, I fear that, with the lapse of time, someone will say: we do not find the ruling of stoning in the Quran. Then, they become astray due to giving up one of the obligations that Allah, The Exalted, has revealed.”

The stoning is due upon a married person (whether a man or a woman) who commit Zina if there is a clear evidence, or pregnancy, or confession. The Prophet read the verse of stoning to death as (what means): “If ash-Shaykh and al-Shaykha (i.e. a married man/woman) commit Zina (adultery), you have to stone them to death as a form of torture of Allah. And Allah is The Almighty, The All-Wise.” [Al-Bukhari and Muslim]

Allah knows best.