I've never had an SD card fail and I've had mixed results with free data recovery software on the 'puter.
This alone qualifies me as an EXPERT in data recovery.
There is however, one GRAND POOBAH of data recovery on this board by the name of Evo.
You may want to consult with him first.

This guy from the Interwebz has put together a tutorial using
free software from Recovering-Deleted-Files.net


Looks easy enough and the price is right....
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NO STEP ON SNEK