Hi @Rajib Deb In addition to @GeethaThatipatri-MSFT . You can refer to the following documentation for more details.
https://learn.microsoft.com/en-us/azure/cosmos-db/scripts/powershell/cassandra/create
Write-Host "Creating keyspace $keyspaceName"
$keyspace = New-AzCosmosDBCassandraKeyspace -ParentObject $account `
-Name $keyspaceName
Regards,
Oury