Jeremiah 29:10 For thus says the LORD: After seventy years are completed at Babylon, I will visit you and perform My good word toward you, and cause you to return to this place. 11 For I know the thoughts that I think toward you, says the LORD, thoughts of peace and not of evil, to give you a future and a hope. 12 Then you will call upon Me and go and pray to Me, and I will listen to you. 13 And you will seek Me and find Me, when you search for Me with all your heart. 14 I will be found by you, says the LORD, and I will bring you back from your captivity; I will gather you from all the nations and from all the places where I have driven you, says the LORD, and I will bring you to the place from which I cause you to be carried away captive.
Jeremiah 29:10 wouldn’t indicate that but maybe 12-14. Many theologians see those verses applying to yet another period in time, when the UN re-established the nation of Israel in 1947. Otherwise, if it referred to the return from Babylon, the fulfillment would not be exact due to the plural of “nations”. The other tribes were taken captive by Assyria and were not returned from captivity. Only the re-establishment of Israel as a nation fits this prophecy.
I believe that the number seventy symbolizes completion and fulfillment of God’s sovereign plans for creation and all of human history. The completion of the years of the kingdom of Babylon would also be the completion of Judah’s exile.