@Spaghettification, it's not a set number of games. It's a matter of how much confidence the system has in your rating.
How the confidence gets measured is complicated. If you want to you can read about it in the link
@MoistvonLipwig provided.
To see how close you are to being non-provisional, click on your name, go to your profile, then choose the type of game on the left. You'll see a page with both your rating and the rating deviation. The higher the deviation number, the less confidence the system has.
When it reaches 110 or less you're no longer provisional.