There are 2 airports in Argentina: Ezeiza international airport and Jorge Newbery aeroparque for domestic flights.
If your domestic flight leaves from aeroparque , you have several transport options to move from one airport to the other:
-Manuel Tienda Leon transfer: (there is a desk just outside the baggage claim in Ezeiza) or you can contact them in advance : www.tiendaleon.com. This option is cheaper than a taxi however they have a fixed timetable.
-Taxis: there are plenty of taxis outside the airport. All of them are secure and safe. UBER also operates in buenos Aires