You can find the Unmanaged Bot in the settings tab of Teams Manager, specifically in the Expert mode.
Here's how to access it:
Open Teams Manager
Click on the hamburger menu in the upper left
Select "Settings"
Click on "Expert mode"
In the settings sidebar, look for "Unmanaged teams"
This is where you'll find the Unmanaged Bot feature, which allows you to convert existing unmanaged teams into managed teams that comply with your governance policies.