Please read the following user tip and restate your question/problem in detail: Writing an Effective Apple Support Communities Question - Apple Community
Does your scanner save the scanned images to the Sandisk card? Does your iMac have a built in card reader? If it is are you using your iMac's card reader to copy the image files to the Desktop? Or can you set the scanner to save the scanned images directly to the Desktop in it's preferences?
If the iMac doesn't have a built in card reader you can get an SD card reader to connect via USB and use that.
