Even in prison, the fullness of the love of God can be felt.

In paragraph 201, it is revealed to St. Faustina that "Now I understand that even in prison there can burst forth from a pure heart the fullness of love for You, O'Lord"
External things mean nothing to pure love.
Dear God,
Please show yourself to those in prison. Show your mercy to them. Whatever I have done, whatever prisoners have done, if they turn to God with a contrite heart and full intention to love and try to amend their life, then God is waiting to shower them with love and mercy. Nobody is outside the love of God. It is up to us to turn towards Him. Amen