Adobe Fireworks allows you to perform batch processing. So you can convert, resize, ... multiple images in seconds.

To use this feature, go to the menu "File -> Batch".
Then, select the images you want and click "Next".

Note : To select all the images in a folder, you can click "Add all" then, click "Next".

In the next window, you will be able to perform certain actions present by default in the program.
In our case, we will convert all our images in jpg. To do this, select "Export" and click the "Add >" button.

Then, select "JPEG - Better Quality" in the list. Then, click on "Next".

You can save this script by clicking "Save Script" if you wish.
Then, click the "Lot" button.

Now, Fireworks will convert each image in jpeg. And it will not take you more than 30 seconds. (The time depends on the number of images and actions to take.)

Now that the image processing is finished, all our images were converted to jpeg and the original files have been moved to an "Original Files" folder.