Older auto-backups for Word documents (.asd) can probably be only recovered using those older versions of MS Word, thus up to version 2007. Once recovered, you can save the document in various formats, including plain text.
Without the proper version of Word, it will be very hard or perhaps impossible to recover and convert documents from the .asd backup and as far as we know, no dedicated utility for asd to txt conversion or any similar conversion actually exists.