Hello again, sallenmanagement. I appreciate your prompt response and providing additional details about your concern. 

When deciding to cancel your QuickBooks Desktop (QBDT) account, you'll need to gather all data and reports. Since once the plan is cancelled, and you can't renew, you can no longer access the company file. 

As for your years worth of attachments, you may consider looking for a third-party app. There could be a compatible app that can attach those to your transactions, so you no longer need to do it manually in QuickBooks Online (QBO). For guidance, go to the Apps.intuit.com  to see the list of the apps that work in the system.  

If there's anything else I can do for you, let me know by commenting below. I'd be more than happy to help. Take care.