Personally I wouldn't dream of pacing the effort on a power number, it seems this second race of the day - and unless the OP has very good knowledge of how that race, and that recovery will have impacted his power then picking a number is more of a lottery on blowing up as just riding it on feel after getting some decent experience. Also as it's a time period that is rarely done, you probably don't have a whole lot of data, and it's potentially very sensitive to conditions - prologues are often point to point and the difference between a tail wind and a head wind could be over a minute difference to your time.
For me - I went in to an 11 minute TT, with little idea of what I could do - 340w for 22minutes, 400w for 6 minutes were the only really testing sides. It was an undulating course and I paced it on RPE - hitting the uphills harder the downhills, my first 20seconds up a hill and to get up to speed were 700 watts, holding back to threshold there would've not helped my time I'm pretty sure, the next 3minutes on the flat was 380, 80 seconds at 420 up a hill. 2minutes at 310 downhill (some zero in here as I spun out the gear I had and just tucked) 1:50 at 400 uphill. 90 seconds at 310 downhill, and 80 seconds at 410 to finish on the flat. An overall 380 average. It was a good workout (didn't get me anywhere near the money though) But I spend very little time riding either to a power number - I had no idea 380 was achievable, and there's certainly no time to hold back in such a short event.
I think the most important advice to the OP is to work on position and equipment, particularly if the stage race rules say road bikes only (as is common) as you can make big improvements on your normal comfortable road race set up for a 10 minute effort.