Updated reminders
If you upgrade your account in the Reminders app on a device with iOS 13, iPadOS 13, macOS 10.15, or later, you see updated reminders on iCloud.com. To see which version of Reminders you have, look for one of the following:
If you’re using updated reminders, you see at the top-right corner of each reminder list.
If you’re not using updated reminders, you see Options at the top-right corner of each reminder list.
After you upgrade, you can view your reminders on iCloud.com and on your devices with iOS 13, iPadOS 13, macOS 10.15, or later where you’re signed in to the same Apple Account. If you also have devices with earlier versions of iOS or macOS, you don’t see your updated reminders on those devices.
See the Apple Support article Update the Reminders app in iOS 13 or later.