SB 10.50.57

tatra yoga-prabhāvena
 nītvā sarva-janaṁ hariḥ
prajā-pālena rāmeṇa
 kṛṣṇaḥ samanumantritaḥ
nirjagāma pura-dvārāt
 padma-mālī nirāyudhaḥ
Synonyms: 
tatra — there; yoga — of His mystic potency; prabhāvena — by the power; nītvā — bringing; sarva — all; janam — His subjects; hariḥ — Lord Kṛṣṇa; prajā — of the citizens; pālena — by the protector; rāmeṇa — Lord Balarāma; kṛṣṇaḥ — Lord Kṛṣṇa; samanumantritaḥ — advised; nirjagāma — went out; pura — of the city; dvārāt — by the gate; padma — of lotus flowers; mālī — wearing a garland; nirāyudhaḥ — without weapons.
Translation: 
After transporting all His subjects to the new city by the power of His mystic Yoga-māyā, Lord Kṛṣṇa consulted with Lord Balarāma, who had remained in Mathurā to protect it. Then, wearing a garland of lotuses but bearing no weapons, Lord Kṛṣṇa went out of Mathurā by its main gate.
Purport: 

Śrīla Viśvanātha Cakravartī quotes the following verses from Śrī Padma Purāṇa, Uttara-khaṇḍa, to describe how Lord Kṛṣṇa transferred the citizens from Mathurā to Dvārakā:

suṣuptān mathurāyān tu
 paurāṁs tatra janārdanaḥ
uddhṛtya sahasā rātrau
 dvārakāyāṁ nyaveśayat

prabuddhās te janāḥ sarve
 putra-dāra-samanvitāḥ
haima-harmya-tale viṣṭā
 vismayaṁ paramaṁ yayuḥ

“In the middle of the night, as the citizens of Mathurā slept, Lord Janārdana suddenly removed them from that city and placed them in Dvārakā. When the men awoke, they were all amazed to find themselves, their children and their wives sitting inside palaces made of gold.”

Thus end the purports of the humble servants of His Divine Grace A.C. Bhaktivedanta Swami Prabhupāda to the Tenth Canto, Fiftieth Chapter, of the Śrīmad-Bhāgavatam, entitled “Kṛṣṇa Establishes the City of Dvārakā.”