You need to configure an order status of the "Order picked up" type (it can also be an existing status).
This is the final status of an order AFTER the customer has picked it up via Click & Collect.
PrestaShop 1.7, 8 and 9: Store Settings menu / Orders / "Order statuses" tab
Important : the following options MUST be checked in the relevant status:
- Consider the associated order as validated
- Mark the associated order as shipped
- Mark the associated order as paid