For vCenter, you need to enable port 443. Additionally, VMware Converter requires a direct connection to the ESX server, so for ESX, you need to enable ports 443 and 902.
but It is recommended to install VMware Converter near the destination so better install VMware converter in your vCenter and If you have a firewall in the Cloud, allow incoming traffic on ports 22 and 443. For Windows conversion in proxy mode, install the VMware Converter agent on your source VM and allow traffic on port 9089.