How were you accessing the files in the first place? Microsoft doesnt natively save to Dropbox via a computer.
You should have all files at www.dropbox.com/home. You can also see what has happened to files at www.dropbox.com/events.
The other question is 'how long?' since you accessed the files? Was your last log in over 12 months? If so files are removed for inactivity and so not recoverable I'm afraid.
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