You'll need a w/Y-splitter OTG(On-The-Go) cable , you can search that up on amazon or snapdeal .It's same as a normal OTG except that it has an extra outlet for power source , also your smartphone should be OTG compatible.. you will get for as low as Rs 200-250/-Connect one end of the cable to your phone…another end to any powersource (Powerbank will do)….and then connect your Hard disk to the usb-slot end of the cable
After connecting, you’ll need a file manager app to access the hard disk…any app will do but i would personally suggest “ES file explorer”
You can now buy new or refurbished DELL 1.2TB 12G 10K 2.5 SAS HDD 099X7T at best price in India.