Good to have you back here, Ruben.
Once you upload a file in QuickBooks, it will be stored in the Attachments feature within QBO. You can use this option in retrieving your files to get the data you need. The steps are simple and pretty easy. Here's how:
For the details of the transaction, you can go directly to the Expenses tab and select Vendors. Select the Vendors name, then from the Transactions List, simply select the type of transaction.
With these instructions, you'll surely get those information that was not carried over after converting your sub-customer into a project.
Please click the Reply button if you need more help.