Hello Imnioi, 

Welcome to the Community page, 

If you click on sales>all sales>click on the filter so it is just invoices showing and the date range and customer you need then, on the right-hand side is an icon that is a rectangle with an arrow going out that is the export button if you click that it will export out of QuickBooks whatever invoices are showing in the all sales section. 

You can not export the invoice within the invoices the only way is though all sales.