Set up inventory tracking
Accurate inventory on your Shopify store helps customers when they're trying to place an order. Before you can view or adjust inventory levels for a product, you need to set up inventory tracking for that product. When you track inventory for a product in Shopify, you can view the history of inventory for that product for up to the most recent 90 days.
If you want to continue selling products that are out of stock, then check Continue selling when out of stock.
Steps:
If a product's inventory quantity is tracked using inventory apps, then its quantities are allocated only to that app location. You can change the locations that products are assigned to.