Is there a free app to track your sleep with Apple? I don’t know when pillow stopped tracking it or when you had to start paying for the free features.

You can use the built-in sleep tracking functions in Health (see the article linked to above). If you don't have an Apple Watch, the data collected is limited.

There are lots of sleep-tracking apps in the App Store. Some of them have a one-time fee, and some of them have subscriptions with free trials. Some of them allow access to a limited feature set for free. One I've always liked is AutoSleep. I believe it has a one-time fee.