I'll assume you're talking about malted millet, not plain millet.
If you look around there are some numbers but nothing concrete like you get for barley malt. It also varies quite a bit by maltster (eg CMC is reported to be less than Grouse) and hugely by your mill gap and mashing methods.
PPG is supposed to be 25 to 32 depending on your mill gap, and then you have to mash it correctly too. Which is harder than barley due to the higher gelatinization temp of millet, which denatures the enzymes that make fermentable sugar. Look for the Lavery method for mashing.