I have been using Assura 3.1 for DRC,LVS and extraction for 0.35 um cmos process and now we have been using 65 nm process.
Does this Assura is capable for DRC, LVS and including extraction for 65 nm cmos process.
First of all, Assura 3.1 is no longer supported. The currently supported version is 4.1, so you really should use that. That's the only version available on http://downloads.cadence.com .
Secondly, it's not really a matter of Assura 3.1 being "capable" for 65nm. What matters is whether the foundry you're using has qualified it for their specific 65nm rules. But I really would suggest you install 4.1. There really is no good reason to use an old version.