I have resolved this issue. My learnings so far...
CURL command accepts thumbprint in the command line instead of certificate files. We need to mention the thumbprint using the certificate store path. To get the certificate store and thumbprint run the following command in the powershell.
cd Cert:\LocalMachine\My\
Get-ChildItem -Path Cert:\LocalMachine\My\ (To get the certificate thumbprint)
PS Cert:\LocalMachine> curl.exe -X PUT -H "Content-Type: application/json" -d '{"DatabaseName": "DB_Name"}' --cert "LocalMachine\My\xxxxxx" --key "D:\RavenDB\certificates\xxx.key" https://xxx:000/admin/databases
This is the command which finally worked to create a database using CURL Command in Ravendb.
Thanks Kannadasan