How can I recover my lost data for free?

You can use Soouya RecoveryMaster to get the data back as long as your it has not overwritten by new data. There is a trail version (free for 10MB) available of this software to download on your PC and you can connect the storage drive that contains your lost data. Then, you can use the program to scan the and recover your files. At last, you can check your recovered files and select a location to save them.