There is a standard field in the invoice called {quantityordered} which shows the sales order total quantity per item line. But we cannot have the option to fetch it through the transaction search directly. So we need to apply the join field applied to the transaction and fetch the quantity from there.
Search result screenshot.
But when we fetch the result by this join will give duplicate values in the search result. We have to group the result;t by line id and fetch the maximum value for the quantity.