I probably can't speak, as I'm currently on a chaotic pattern that averages out as 3am to midday sleeping, with a nap at some point, but…
I have a lot of experience with this, and have found that if my sleep pattern is as reversed as yours is, there are 2 options. 1: push through an entire overnight, then get to bed about 12 hours before you want to wake up the next day. 2: push your bedtime back about an hour a day i.e. an hour later each day, until you've reached the right bedtime.
Either way, be ruthless about your sleep hygiene for about a week afterwards. If you have sleeping meds, use them to help cement the new pattern. Any other things you generally do to sleep - baths, hot drinks, whatever - schedule them and stick to it.
The other very important thing is mealtimes. Google for info for people with jetlag; this will explain what to eat and when, when establishing a new sleep pattern. That really helps.