A POST
call against /api/order
will trigger the creation of a new order, hence the missing required field errors. See https://shopware.stoplight.io/docs/admin-api/52ce9936f6ea4-create-a-new-order-resources
If you want to search for an order more specifically, you need to use the api/search/order
endpoint. See https://shopware.stoplight.io/docs/admin-api/0b7d9d489b841-search-for-the-order-resources