Open the Compressor program.
Drag the files you want to covert from the folder to the DropZone (down arrow) in the batch window.
In the Settings window of Compressor, choose QuickTime and the version of ProRes you want, drag this to the the clips you put in the batch window.
Click Submit
This will convert the files to ProRes and put them back into the same folder. Also, preserving your original files.