Great to have you here, JaneJJ.
We can import your invoices to QuickBooks Desktop 2013 using an Intuit Interchange Format (.IIF) file. We can convert the Excel file to IIF format to import and export invoices to and from QuickBooks Desktop. I'd suggest visiting the Intuit Marketplace to see applications that you can use in converting the file.IIF.
Once you convert it, follow the steps below to import the invoice transactions:
For more details about this one, see Export or Import Intuit Interchange Format (.IIF) Files article. Please note since you're using an older version of QuickBooks Desktop, the steps above may or may not work. Feel free to our Bring in your data page for more insights about importing your data to QuickBooks Desktop.
I'd like to know how you get on after trying the steps, as I want to ensure this is resolved for you. Just reply to this post and I'll get back to you. You have a good one.