Hello,
Two suggestions, not sure if they will work for you but  if that data 
retention is critical you could explore
1. Shift your current dB to NFS like share mapped to the existing backup 
server, then import this share on the new box, since both talk NFS may be 
it will be successful, once you can see the same dB on the new server, you 
could copy to local and do your restore.
2. what is you could migrate the existing dB to a new test Linux server, 
where it can live it's useful life for reference ?
3. Retain the existing backup server till dB is retired ( may be 
impractical, as you will tie up the server , but it's an options 
nevertheless)
HTH

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