Just take your 4×6 photo, run it through the photo scanner, and then transfer it over to the photo frame.
This is an ideal match, as it essentially allows you to handle the transfer of your photos from one format to another and to start displaying them immediately! This product is not just a single scanner, but actually a “digital photo kit” that combines a photo scanner with a digital photo frame. Plustek Photo Digital Kits – CCD Photo Scanner with Feeder