Orders on Shopify and Amazon have a unique order ID.
For each order that is shipped via FBA, the app provides an option to configure the order ID on Amazon. You can pick between 2 values that can be saved as the order ID on Amazon:
Option 1 - Shopify Order ID
Option 2 - Shopify Order Number
Shopify Order ID is the unique numeric code that Shopify attaches to each order. This number cannot be altered.
Shopify Order numbers start at #1001 by default. While you can’t change the order number itself, you can add a prefix or suffix to create IDs like "EN1001" or "1001-A."
To configure the Amazon Order ID go to Shipr app > FBA > Settings > Pick the value for Amazon Order ID: