The three lokas are Gokula (Goloka), Mathura and Dvaraka. Krsna lives eternally in these three places

Expressions researched:
"The three lokas are Gokula (Goloka), Mathura and Dvaraka. Krsna lives eternally in these three places"

CC Madhya-lila

The three lokas are Gokula (Goloka), Mathurā and Dvārakā. Kṛṣṇa lives eternally in these three places.

CC Madhya 21.91, Translation and Purport:

“The three lokas are Gokula (Goloka), Mathurā and Dvārakā. Kṛṣṇa lives eternally in these three places.

Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura comments that in the Goloka planet there are three divisions: Gokula, Mathurā and Dvārakā. In His incarnation as Gaurasundara, Lord Śrī Caitanya Mahāprabhu, the Lord conducts His pastimes in three areas: Navadvīpa, Jagannātha Purī (and South India) and Vraja-maṇḍala (the area of Vṛndāvana-dhāma).