conversion of bsnl connection from 2G to 3G without changing SIM

I am having Nokia Lumia 710 Windows Phone. At present I am 2G SIM.
My phone is 3G support phone. On my service providers bar it is
showing 3G. I do not know whether it is actual 3G. Can I have
Video conference. If yes what should I do to achieve it and other
3G facilities.

you don't need to convert it to anything, all you need to do is 3G recharge and 3G will work on you. However, you need to make sure that 3G is present in your area. If it shows 3G on in your phone then its 3G available, just make 3G recharge and enjoy faster speed.