To export ESX(i) using vicfg-cfgbackup configuration you will need VMware vSphere CLI (vCLI). If it is not installed, please do that now. Once installed, open CLI and type the following command:
C:\Program Files (x86)\VMware\VMware vSphere CLI\bin>vicfg-cfgbackup.pl --server esxhost.domain --username root --password YourPassword -s C:\esxi\esxhost