You need to remove the line number 1 from the file C:\Users\PC\.ssh\known_hosts, save it and then try ssh again.
This QNAP model should be x86_64 based, so the identity_linux_amd64 is the right one.
However, I would suggest to create an identity on your PC, so you need to download a binary for Windows: Identity - Node Operator
And follow this guide further.
If you have one identity already, you need to use a different name, for example “storagenode2”, and folder will be C:\User\PC\AppData\Roaming\Storj\Identity\storagenode2
When you would have a generated and signed identity, you can transfer this folder to QNAP.