I don't "think" there is any command going to tell you that. The "snmp" command itself has no version option.
1. I found the best DOC on snmp to be this TR -> http://www.netapp.com/us/media/tr-4220.pdf
It says OnTAP supports versions 1,2c,and 3.
And its a recent TR (2016).
2. Other quick online info can be had from the man pages but it also doesn't go into version or how to determine.
cluster> man snmp