It cannot be retrieved like you think nor is there a specific upgrade since you are dealing with two entirely different platform types.
QBSE is single entry and the rest of quickbooks is double entry. Unless you exported to excel and entered the second half of double entry prior to import you are guaranteed to lose data.
That being said - you still have 365 days of reports only access to QBSE and you could have exported transaction lists to excel before cancelling your QBSE.
If that is not enough you can resubscribe for a month to retrieve individual data snippets but do use copy/paste between multiple open browser windows to migrate your missing data
Good Morning, @alysa5683.
It's always nice to see a new face in the Community. Yes, that's correct @john-pero. There isn't a way to upgrade from QuickBooks Self-Employed to QuickBooks Online because they're two different product platforms. The only way to export and import the information is by using an Excel CSV file. However, ChronoBooks is designed to help people export their company data from QBSE to QBO. Other customers have found it helpful to use ChronoBooks to retrieve that data or move it from one account to another.
Here's an extra link that can help you export and import your company data.
If you have any more questions, please let me know. I value you and the success of your business. Happy Tuesday!