If you know an invoice number, but need additional information on which fair or employer it is for, you can use the Explore Insights feature to look up this information.
Go to the Career Fair base once you're in Insights, and select the Registration Invoices drop down then select Number as a filter. You can then enter the necessary invoice number in the filter.
Then select the fields of information needed for the invoice, such as career fair and employer name. This is an example report that you can use to pull this information quickly.