This means that you will no longer be able to access your notes and lists from assistant.google.com/lists/mainview or shoppinglist.google.com. Instead, you will need to use Google Keep to access new and old lists created with the Assistant.
However, there are a few edge cases where your notes and lists might not be moved, such as family notes created on Smart Displays that have a large amount of items or characters. In these rare cases where the notes or lists are not moved automatically, Google will have this data available for users to download through Google Takeout until May 1, 2024. Note that after this date, the data will be automatically deleted from Google’s servers.
Old Shopping List and new Keep setup via Assistant Settings