These options are available for single images, but can be applied to batches of images as well. To do this, instead of opening a single image at a time, select a number of them in the Finder and likewise right-click to open the selection in Preview.
When opening them in this manner, they will be gathered in a single Preview window that will list them as thumbnails to the left of the main viewing area. With this view, you can then hold the Command key and select some of the images in random order, use the Shift key to select a series of images in order, or select one and then press Command-A to select all of them.
With your desired images selected, the Export option in the File menu will change to Export Selected Images, which will give you the same options to save them in the desired format. Do keep in mind that when using batch conversions you will not be able to name the files differently, so they will keep their original names but have a new file type suffix associated with them.