How many thylacines were there in the 1000th century?

Answer 1

The Thousandth Century isn't here yet. Perhaps the questioner means the year 1000? If so, we can't know, because Tasmania was undiscovered (at least by anyone who could leave notes on the census) then. Thylacines (or parts of them, in traps) were last seen in 1957, so we think they're extinct.

They were apex predators, so there were never very many of them, even in their heyday, whenever that was.