How to check SNMP SHA and AES password in Fortigate

Hello Umesh.
Could you please elaborate more on the issue?
May I know if you are talking about the FortiGate admin password or any other configuration related password ?

You mean can you decrypt the SNMPv3 passwords stored in configs? I doubt so, as if I remember correct only passwords' hashes are stored in the configuration, if it is so  then they are non-reversible.

Check it on your SNMP server side, otherwise you have to reset it on both sides.