Create a reminder from a conversation in Messages on Mac
When a message contains a request to do something at a particular time (for example, “Call me at 6:00 pm”), you can create a reminder.
In the Messages app on your Mac, select a conversation.
Look for the message with the request, then Control-click the underlined text and choose Create Reminder.
A reminder is also created automatically when someone asks you to do something (for example, “Can you get milk tomorrow?”) and you provide an answer (such as “Yes”, or something similar). The suggested reminder appears in the Reminders app in Siri Suggestions.