That just means 8.64 acres.  India has a capital gains tax, but unfortunately for you, it doesn't apply to farm land.  Adjusting for inflation won't tell you much, unless you also adjust for currency fluctuation.  But farm products have suffered from deflation the past couple years in India, so farm land may have followed that trend.

If the value of the land had gone down since 2016, I would expect a client to tell me that sad story.  If it had increased greatly, perhaps because it became more likely to have rezoning approved, I would expect a client to be reluctant to fill me in on those details.  Your starting point is zero basis.  Tell that to your client, and then listen for helpful facts that IRS would accept in an audit.  Why wasn't it sold in 2016?  Why was it sold in 2019?