cab to 7-zip conversion esentially represents repacking compressed archive from Windows Cabinet format (.cab) to 7-zip (.7-zip) format. The most convenient way to convert cab to 7-zip would be to use a program that supports both of these compression formats, for example 7-zip or ALzip. But of course you can use one software to extract the contents of .cab file and use another to compress the files using 7-zip.
Worth mentioning is that 7-zip archives use like half dozen of various extensions for default archive, so sometimes a simple rename may associate you 7-zip file in your file manager.Open CAB file Open 7-ZIP file
Popular open source file archiver with a high compression ratio