You can create a unique alphanumeric SKU for each product to efficiently track inventory and manage sales.
How to add product's SKU
Go to Admin > Products > All and click on
Add productor choose any existing product that you wish to edit.
Go to the "Inventory" section and fill in the SKU. Click
Save.
SKU will be shown on the Storefront and Invoice.
You can also edit your SKUs in bulk using bulk edit function.