Here "free from sin" is a metaphor for them no longer having a strong desire to sin and therefore being able to stop themselves from sinning. You can translate this in an active form. Alternate translation: "Christ has freed you from sin" or "Your strong desire to sin has been taken away" or "You have been made free from sin's control over you" (See: [[rc://en/ta/man/jit/figs-activepassive]] and )
Slavery of righteousness is a metaphor meaning having a strong desire to do what is right. It is as if righteousness controls the person. Alternate translation: "you have been made like slaves of righteousness" or "you are now controlled by righteousness" (See: [[rc://en/ta/man/jit/figs-metaphor]])
This can be stated in active form. Alternate translation: "Christ has made you slaves of righteousness" or "Christ has changed you so that now you are controlled by righteousness"