The Shopify API provides multiple order identifiers that you can export. 

Below are the related fields you can select in EZ Exporter:

• id - The auto-generated ID assigned by Shopify mainly used for API purposes (e.g. 2205783916624).
• order_number - The order's position in the shop's count of orders (e.g. 1001).
• name - The order name, generated by combining the order_number property with the order prefix and suffix that are set in the merchant's general settings (e.g. #HA-1001-US).

In most cases, you'd want to select the field called name, which is the order number/ID displayed in the Shopify Admin > Orders page.