Never do anything directly on a live store. First setup and test on a development domain (i.e. “dev.url.com”).
Temporarily disable Magento cache
To avoid any possible issues with the installation we recommend disabling Magento cache before proceeding with the installation and re-enabling it once the install is complete.
Upload Acx Customer Order Number
Using your favorite FTP client, upload all files and folders to the root folder of your Magento installation
Go to “Stores->Configuration->Acx Extension->Order Number from admin panel
Invoice Number setting: You can set invoice number from here.
Shipping and Memo Number Setting: You can set shipping and memo number from here.
After completing admin configuration. In the frontend when a customer place an order, they will see the order number format as like the screen-shot.
Thank you for reading this user manual! We'd be glad to help you if you have any question relating to this extension.