A fault with the display function of a digital photo frame is unlikely to impact upon its ability to store photos, so your images should still be there (and fully accessible).
I assume that you got the images onto the device by connecting it to a PC with a USB cable. If so, it should be just as easy to move images in the opposite direction. So connect the device to your PC/laptop with a USB cable. If a dialogue box appears, asking you what you want to do, select 'Open folder to view contents'. (If you don't see a dialogue box, go to 'Computer' and look to see if the device is shown there as an external drive. Assuming it is, double-click on it).
You should then be able to drag-&-drop (or copy-&-paste) files which are on the device to anywhere you choose on your PC/laptop's hard drive, or to a USB pen drive attached to it, in the same way that you can move any other files around with Windows.