How can I import transport from same external system

My Abaper asked me to import transport from different system with same name.

1) The same transport numbers have already been created in our system and have been imported in our system.

2) I tried overwriting cofiles and data files using cg3z.

3) But I am not able to over write the transport. When I select Ectras>Other request>Add. It adds the request for our existing system.

How can I import external request to our SAP system?