Now these are the words of the letter that Jeremiah the prophet sent from Jerusalem unto the residue of the elders which were carried away captives, and to the priests, and to the prophets, and to all the people whom Nebuchadnezzar had carried away captive from Jerusalem to Babylon;
Jeremiah 29:1 Now these are the words of the letter that Jeremiah the prophet sent from Jerusalem unto the residue of the elders which were carried away captives, and to the priests, and to the prophets, and to all the people whom Nebuchadnezzar had carried away captive from Jerusalem to Babylon;
Jeremiah 29:2 (After that Jeconiah the king, and the queen, and the eunuchs, the princes of Judah and Jerusalem, and the carpenters, and the smiths, were departed from Jerusalem;)
Jeremiah 29:3 By the hand of Elasah the son of Shaphan, and Gemariah the son of Hilkiah, (whom Zedekiah king of Judah sent unto Babylon to Nebuchadnezzar king of Babylon) saying,
The verse centers on "words", "letter", "jeremiah", "prophet", "sent", "jerusalem", "residue", and "elders". It is saying that the verse draws attention to "words" and "letter", so its meaning should be read from those terms before moving to application.
The next verse adds "After that Jeconiah the king and the...", so "words" and "letter" should be read forward into that movement. In Jeremiah context, the local focus is covenant, worship, and faithfulness.
A plain takeaway is to answer the verse's own emphasis on "words" and "letter" with trust shaped by these words, not by a vague optimism outside the passage.