Secure Copy uses ports 135 through 139 (both TCP and UDP).
SMB port 445
Port 25 (SMTP) is used for email.
Please note, ports 137 and 138 can be closed if needed. Blocking ports 137 and 138 should not have an impact on copying data from the source to the target. By blocking these ports you will will not be able to browse the Network (In the copy locations, click Browse | expand Network) as Windows uses port 138 to populate the browse list under Network in Windows File Explorer (which SC leverages).
You may also have an issue with specifying a source or target as \\computername\path as port 137 is used by Windows for NetBIOS name resolution. If this is an issue, you should be able to use \\FQDN\path, \\IPaddress\path or put entries in the hosts file for the machine names.