Hi i will buy a apm2.8
is this the place to download autopilot software?
http://firmware.ardupilot.org/Tools/APMPlanner/
and here lot of files and folder. which one i download to my computer?
No, the place to download firmware is:
http://firmware.ardupilot.org/
Then select the vehicle type you want to use.
Start with a Ground Control Station Application which will allow you to flash the Flight Controller with the proper firmware and configure it for your craft. If you want APM planner it’s here:
http://ardupilot.org/planner2/
Mission Planner here:
http://ardupilot.org/planner/docs/common-install-mission-planner.html
QgroundControl here:
http://qgroundcontrol.com/downloads/
You are in an Arducopter thread so I would start with Mission Planner.