An AxCrypt-encrypted file is just a file, nothing else. Just copy them to the USB stick and delete them appropriately from the PC after verifying that all was successfully copied, like would with any file you want to move from one media to another.
Ensuring that “no traces” remain afterwards, requires more tools than AxCrypt. While AxCrypt Premium can wipe the files so they are not recoverable by any regular utility, “no traces” requires more and may in fact be hard to achieve. So it depends on what you really mean with “no traces”.
In general, since they are encrypted, simply deleting them and emptying the wastebasket will take you a long way towards removing most traces, however for example parts of the file name may remain in the file system, and of course the encrypted data – but it’s encrypted so it’s worthless unless the password is known.