Not sure it is possible to check the number of uninstalls - I guess this is a private info of the user.
You can check the number of active users though: add a date-time property “last home screen visit”, update it each time when user visits home screen, and then you can get the info, for example, how many users used your app within last X days.
BTW, don’t forget to “initialise” this property upon user signup (I mean put a current time there) - I’ve seen some cases when property’s value didn’t get updated on the Home screen, when it was empty before.