Hello Salvo
In QuickBooks Online you can import invoices from excel,so in the QuickBooks Desktop product you have the option of exporting the customer transaction detail report to excel (customised to just invoices and the date range you want)
If it is just open invoices you want to import you could use the open invoice report and export it to an excel worksheet.
It may be the case the excel sheet needs some adjustments as regards to the column information.To view what an example of the format QuickBooks Online is looking for looks like you can go to QuickBooks Online >import data>invoices(you can download a sample within that section to view what sections can be imported)
Any questions at all on this let us know
Emma
