How to obtain ImageScan app for Silvercrest Image Scanner

I would highly suggest looking into the most excellent VueScan (https://www.hamrick.com/) scanning application for scanners that are not supported natively by macOS. There is a "supported scanners" search box on that page that you can look for your scanner make/model. If you don't find it, I would contact them as it may be supported anyways. VueScan is a far superior scanning application to those applications that are shipped with nearly any scanner.