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 are using updated reminders, you see at the top right-hand corner of each reminder list.
If you are not using updated reminders, you see Options at the top right-hand corner of each reminder list.
After you upgrade, you may view your reminders on iCloud.com and on your devices with iOS 13, iPadOS 13 and macOS 10.15 or later that are signed in with the same Apple ID. If you also have devices with earlier versions of iOS or macOS, you do not see your upgraded reminders on those devices.
See the Apple Support article Upgrading the Reminders app in iOS 13 or later.