Divide the figure by 50 and you get the number of Contracts bought or sold.
As every transaction shall have one uy and Sell so :
1contract Buy=1contract Sell= Volume 50
Not sure if you are talking about Nifty Futures volume or Nifty spot volume.
If it is Nifty futures - then reply by RKKarnani is the right answer.
If it is about nifty spot = then it is total volume of NIFTY 50 stocks bought= stocks sold = sum of volume of all 50 Nifty stocks traded on exchange today.