John Gill Commentary Deuteronomy 4:29

"But from thence ye shall seek Jehovah thy God, and thou shalt find him, when thou searchest after him with all thy heart and with all thy soul." — Deuteronomy 4:29 (ASV)

But if from there you shall seek the Lord your God
By prayer and supplication, acknowledging and confessing sin, and desiring that God would be gracious and forgive it, and bring them out of their miserable condition; even if out of those depths of affliction and distress, and though scattered about in the world, and in the uttermost parts of it:

you shall find him ;
to be a God hearing and answering prayer, gracious and merciful, ready to help and deliver:

if they seek him with all their heart and with all their soul ;
sincerely and affectionately.