From which place did Saptarishis in boat travel?
As per Śrīmad-Bhāgavatam (Bhāgavata Purāṇa) 8.24,
One day while Satyavrata, the King of Draviḍadeśa, performing austerities by offering water on the bank of the river Kṛtamālā, a small fish appeared in the water in his palms.
Later the fish became bigger and bigger and Satyavrata came to know that the fish is not the ordinary one. Then, Lord said to him,
When all the three worlds merge into the water, a large boat sent by Me will appear before you. Pulling the boat, with you and all the ṛṣis in it, O King, I shall travel in the water of devastation until the night of Lord Brahmā’s slumber is over.
Purport: This particular devastation actually took place not during the night of Lord Brahmā but during his day, for it was during the time of Cākṣuṣa Manu. Brahmā’s night takes place when Brahmā goes to sleep, but in the daytime there are fourteen Manus, one of whom is Cākṣuṣa Manu. Therefore, Śrīla Viśvanātha Cakravartī Ṭhākura comments that although it was daytime for Lord Brahmā, Brahmā felt sleepy for a short time by the supreme will of the Lord. This short period is regarded as Lord Brahmā’s night.
Later, on the day of Pralay:
As Satyavrata remembered the order of the Supreme Personality of Godhead, he saw a boat coming near him. Thus he collected herbs and creepers, and, accompanied by saintly brāhmaṇas, he got aboard the boat.
The Fish chapter of Agni Purana also mention about Kritamala river. Presently the Kritamala River is known as the river Bhagai or Vaigai and Dravida desha as South India. So answer is South India.
Where did Matsya - fish drop the Saptarishis?
As per The Fish chapter of Agni Purana
Everything happened as the fish had promised it would. The ocean became turbulent and Manu climbed into the boat. He tied the boat to the huge horn that the fish had. He prayed to the fish and the fish related the Matsya Purana to him. Eventually, when the water receded, the boat was anchored to the topmost peak of the Himalayas. And living beings were created once again.
The wiki on Matsya also says the same,
The fish carries the boat with Manu to the high grounds of the northern mountains (interpreted as Himalayas).