If the purchase was finalized in your name before the bank became involved, this differs from a standard Murabaha transaction where the bank buys the asset and then sells it to you.
Don't try to "go back in time" and convert an old purchase into a Murabaha.
Tell the bank from the beginning whether the asset was actually purchased or just reserved or quoted, so they can determine the appropriate structure.
The figures, fees and limits in this answer vary by bank and change over time — confirm them with your bank or the official source before acting.