Both PC and Mac Book cannot detect iXpand Flash Drive

if the iXpand is still detected by an iOS device you can use the app to delete the pictures. The app does not support formatting. if you are worried about the files being recovered after deleting you could lock them (which will encrypt the files) then the files would not be recoverable without your password. other than that contact sandisk support. They have a process for products that have sensitive data on them.