بِعَادٍ

بِعَادٍ is a phrase (شِبْهُ الجُمْلَةِ) consisting of a particle of pulling down (a preposition) and a genitive noun

Phrase		Particle / Noun		Noun		Particle
شِبْهُ الجُمْلَةِ		جَارٌ وَمَجْرُوْرٌ		اسْمٌ مَجْرُوْرٌ		حَرْفُ جَرٍّ
Phrase		Compound		Genitive Noun		Particle of pulling down/Preposition

with Aad	–	بِعَادٍ	=	عَادٍ	+	بِ
		with (the people of) Aad		(the people of) Aad		with

Surah/	Below is the only verse in the holy Quran containing the phrase	بِعَادٍ
Verse

89-5	Did you not see how your lord dealt with (the people of) Aad	أَلَمْ تَرَ كَيْفَ فَعَلَ رَبُّكَ بِعَادٍ

Valuable resources:

Dictionary of the holy Quran by Abdul Mannan Omar