I tried this site to check https://freebitcoins.com/clamchecker/dig/ but it's saying my account not eligible.
Even I had my wallet address before then may 2014. I don't think Coinbase either give me private keys or will claim clam for me.
There is also other criteria that should be meet in order to get your BTC/LTC/Doge wallet to be funded, not just having or owning the address before May 2014, you need to meet some balance threshold, so your account is not considered a dust holding account, also you need to have that amount in the address at the moment that the snapshot of the different blockchains was taken. I don't use Coinbase but I doubt they give the private keys, even to their "vault" multisignature users, also doubt that "vault" function was around when the Clam distribution was made.
Where is the clam.conf located? Thanks!

Usually on Windows you can find it at this location:
C:\Users\YourUserName\Appdata\Roaming\Clamcoin (on Windows 7)
C:\Documents and Settings\YourUserName\Application data\Clamcoin ( on Windows XP)
For linux you can try to look for this location:
~/.clamcoin/