magento 2 custom invoice number
https://www.cynoinfotech.com/product/custom-order-number-magento-2-extension/
Custom Order Number Magento 2 extension allows admin to customize order number as per store requirement. Also, this extension allows customizing order numbers on invoice, shipment and credit memo numbers. Admin can set order number format using different variables, character, prefix, suffix, date/time, random number and counter as per business requirement. The Magento 2 Custom Order Number extension helps Magento stores change order numbers and add ID prefixes to protect sensitive business data.