SB 8.5.11-12

śrī-rājovāca
yathā bhagavatā brahman
 mathitaḥ kṣīra-sāgaraḥ
yad-arthaṁ vā yataś cādriṁ
 dadhārāmbucarātmanā
yathāmṛtaṁ suraiḥ prāptaṁ
 kiṁ cānyad abhavat tataḥ
etad bhagavataḥ karma
 vadasva paramādbhutam
Synonyms: 
śrī-rājā uvāca — King Parīkṣit inquired; yathā — as; bhagavatā — by the Supreme Personality of Godhead; brahman — O learned brāhmaṇa; mathitaḥ — churned; kṣīra-sāgaraḥ — the Ocean of Milk; yat-artham — what was the purpose; — either; yataḥ — wherefrom, for what reason; ca — and; adrim — the mountain (Mandara); dadhāra — was staying; ambucara-ātmanā — in the form of a tortoise; yathā — as; amṛtam — nectar; suraiḥ — by the demigods; prāptam — was achieved; kim — what; ca — and; anyat — other; abhavat — became; tataḥ — thereafter; etat — all these; bhagavataḥ — of the Supreme Personality of Godhead; karma — pastimes, activities; vadasva — kindly describe; parama-adbhutam — because they are so wonderful.
Translation: 
King Parīkṣit inquired: O great brāhmaṇa, Śukadeva Gosvāmī, why and how did Lord Viṣṇu churn the Ocean of Milk? For what reason did He stay in the water as a tortoise and hold up Mandara Mountain? How did the demigods obtain the nectar, and what other things were produced from the churning of the ocean? Kindly describe all these wonderful activities of the Lord.