Here you can download USB and ADB driver for your A6000 smartphone by Lenovo. This driver will also work for 3G handset. Just download from below link and run it. Remember this driver for only PC Windows.
Lenovo A6000 USB/ADB Drivers ( A6000 Plus )
Windows xp , windows 7 32 and 64 bit, windows 8 , 8.1. for windows 10 stay in touch.