A believer recently answered this question by saying, "My sins are under the blood of Jesus."
"The blood of Jesus Christ His Son cleanseth us from all sin." 1 John 1:7. And God says: "When I see the blood, I will pass over you." Ex. 12:13.
Where are your sins? Each one is written down in God's book; each one will be kept in everlasting remembrance, unless all are blotted out by that precious blood. But when you die where will your soul be? It will either be enjoying eternal happiness, if your sins have been blotted out by the blood of Christ, or suffering in everlasting woe, if they are still written in God's great Book.