example:
E:\androidsdk\adt-bundle-windows-x86_64\adt-bundle-windows\sdk\extras\google\google_play_services\libproject\google-play-services_lib\libs
where
E:\androidsdk\adt-bundle-windows-x86_64\adt-bundle-windows is your SDK directory.
*you should be easier to find out the /sdk\extras\google\google_play_services\libproject\google-play-services_lib\libs folder from there