Short answers, pulled from the story.
Nader Shah invaded India and captured Delhi on the 20th of March 1739. He entered the city after the Battle of Karnal on the 24th of February 1739 and held a durbar the next day to begin the occupation.
Nader Shah invaded the Mughal Empire to fund his expansionist dreams and recover from financial crisis in Persia. Contemporary sources suggest he needed to pay his army and secure a new source of cash after years of constant campaigns caused famine and bankruptcy.
Approximately 20,000 to 30,000 Indian men, women, and children were slaughtered during the six-hour massacre on the 22nd of March 1739. Exact casualty figures remain uncertain because the bodies were buried in mass pits or cremated without proper records.
Nader Shah took the Peacock Throne, the Koh-i-Noor diamond, and the Darya-i-Noor diamond from the Mughal Empire. He also levied an enormous fine of 20 million rupees on the people of Delhi and seized a vast amount of other fabulous jewels.
Nader Shah and his Afsharid troops left Delhi on the 16th of May 1739. Before leaving, he ceded back all territories to the east of the Indus to Muhammad Shah, though Sikhs later seized a large amount of booty from his army.