How can I Export My private keys from Wallet.dat online?
Is there any service which will help me to export my private key from wallet.dat?
Or maybe any ONLINE WALLET where I can EASILY IMPORT MY WALLET.dat?
Don't use any online services to export your private key. It is very risky, they might copy/stole your wallet files.
Follow the guide on the link posted by BitMaxz above. In general, use offline + open source tools like pywallet to export your private key (or use Core if you want to go through the hassle).