Order/Delivery Slot
From Shopnix Help
Where to get Delivery Slot feature ?
A delivery slot refers to a specific time window during which a delivery can be made to a customer. For example, a grocery store may offer delivery slots of 9am-12pm, 12pm-3pm, and 3pm-6pm, and a customer can choose which slot they want their groceries delivered in. This is a way for the store to manage the number of deliveries they need to make during a certain time period, and for the customer to choose a time that is convenient for them to receive their delivery.
Go to Admin > Orders , click on the option (red square in the below image)
You can also change the courier option like below
You can delete all the orders by using 
button.