I can help you retrieve all the deleted transactions within QuickBooks Online (QBO).
If you're using the Advanced version and have a backup company file from before the transaction was deleted, you can restore it. However, if you're using another version, you'll need to re-enter the transaction manually based on the information available in the Audit Log.
Here's how to access the audit log:
Click the Gear icon.
Under Tools, select Audit log.
Filter the appropriate user, date, and event(s).
With the details from the Audit Log, you can then manually re-enter the deleted transactions by clicking the +New button.