Hello, Aunchalee. There are not enough inputs for 100% correct answer)

Suppose, if you have automatically configured the creation of MO upon confirmation of SO (MTO Route or reordering rule), then you can configure a simple automated “To Do” action as in the screenshot below.

To do this you need to go to developer mode, then Settings - Technical - Automated actions and create a new one.

If you set Due date = 0 days, then the system will immediately add a notification to the Activity for the selected customer.

And if you go to the order as an responsible person, you can find what exactly expected from you there.
Responsible user will also receive a notification (by email or internally in Odoo, depending on the user’s preferences)

If your process is more complex, please provide more detailed information.
Have smooth work and a nice day!