Context. Context. Context. The exegete's cheer (learned at Dallas Theological Seminary).
Jeremiah 29:11 is part of a letter written to a people in exile to keep them from being discouraged by their circumstances and deceived by false prophets (vv. 4-9).
And they are given (1) a promise of restoration and (2) a path to attain it.
10 “For the Lord says, ‘Only when the seventy years of Babylonian rule are over will I again take up consideration for you. Then I will fulfill my gracious promise to you and restore you to your homeland. 11 For I know what I have planned for you,’ says the Lord. ‘I have plans to prosper you, not to harm you. I have plans to give you a future filled with hope. 12 When you call out to me and come to me in prayer, I will hear your prayers. 13 When you seek me in prayer and worship, you will find me available to you. If you seek me with all your heart and soul, 14 I will make myself available to you,’ says the Lord. ‘Then I will reverse your plight and will regather you from all the nations and all the places where I have exiled you,’ says the Lord. ‘I will bring you back to the place from which I exiled you.’
The scope of ultimate restoration is expanded by the resurrection of Jesus. But the path to the promise remains the same.
"'When you seek me in prayer and worship, you will find me available to you. If you seek me with all your heart and soul, I will make myself available to you,’ says the Lord" (NET Bible).