To open the source code of a thumbnail image to make the image visible

In 2004 I lost photos by a PC crash, but still have a 7 Mb .psd preview file. Because the photos are (also as small preview images) valuable for me I have restored the file by the company DataRecovery Unfortunately, the program (Adobe album ...?) Provided by Canon at that time is no longer commercially available. Therefore the task is to open the file in such a way that the preview images are visible (for example as jpg).