I work nights, what is the best time for me to sleep, and for how long?

7 hrs. You need 7 hrs of uninterrupted sleep on average. Pick a time when you can consistently go to bed, maybe around 9 am.
7.7 hours. Studies show that on average you need at least 7.7 hours of sleep. I would recommend trying to get your sleep right before you go to work, just as if you were sleeping at night and getting up in the morning to go to work.