For each image in your Pages document, click once on it to get the selection grips, and then click the Image tab in the sidebar. Below the wording "File Info" is a generic icon with the filename adjacent to it. Click on that icon and with one smooth motion, drag and drop that image onto a folder on your Desktop, or even a sidebar folder in the opened Photos application. In the latter case with Photos, it will inform you that one image has been added.
This does not remove the image from the Pages document, but you can achieve that for each selected image with a backspace key. This may require reformatting the text flow depending on the current Object Placement and Text Wrap settings in the Pages Arrange panel.