Hi there, nisarsaeedy.
Welcome and thank you for posting here in QuickBooks Community. I'll share information about the migration policy and upgrading QuickBooks Point of Sale. Then, route you to the right support team to help you with the detailed steps.
When upgrading QuickBooks Desktop Point of Sale with version 19.0, you'll have first to make sure that you meet the minimum system requirements. Then, I suggest contacting QuickBooks Point of Sale Care. They have the tools to assist in sharing all the steps that you'll need to perform upgrading QuickBooks POS to ensure everything is in the good shape.
Once you already upgraded, you’ll receive an email confirmation after your order processes that include your license and product numbers. You can also find them in the Customer Account Maintenance Portal (CAMPs). For additional information, you can click this article: QuickBooks Desktop Point of Sale 19.0 Migration Policy.
Please also refer to this article to see details on how you can always update your QuickBooks Desktop Point of Sale system to the latest release: Update Quickbooks Point of Sale.
If you have any questions or clarifications, feel free to drop them here. I'm always here to provide further assistance. Have a good day.