According to this knowledge base article: http://help.filemaker.com/app/answers/detail/a_id/750/kw/converting FileMaker 11 should be able to convert this file into the new format.
Since it doesn't, I'm wondering if the file might be damaged. Try opening the file in FileMaker 4.01, recovering it and then try converting the recovered copy to see if it converts successfully.
Thank you for responding!
When the old FM files didn't open I went looking on the FM support pages and found the article. I had hoped that downloading the trial version of FM 6 would do the trick, which it didn't.
As to trying to open them with FM 4, well, I don't have that anymore. These FM files are on very old floppy disks. The floppy disks are still intact though as all the other files (MS Word) on it opened flawlessly.
However, I have an old iMac here, still running on OS 8.6, so I thought I would download the trial version of FM 6 for Mac Classic OS and see if I can access the files that way . Will report back.