First of all, I would use a different variable for each folder. Dependiing upon the file type you want to save, you need to define the files parameters. For example if you're saving jpgs:
docRef = activeDocument
var jpgOptions = new JPEGSaveOptions();
jpgOptions.quality = 10;
docRef.saveAs (new File(myFolder +'/' + docRef.name.split('.') + '.jpg'), jpgOptions);
By "load action" are you referring to simply running a specific action, or actually loading it into the Photoshop action list from a .atn file and then running it?
the action i've created, "//load the action to save file" means to load it into the script, and then run it
in the action i created many slices to save the file into 3 differents sizes. However, I'm not sure how to use the script to creat slices that are exactly the same with the previous ones I created.