Although you can repack 7-zip archives (.7-z, .7z, .7zip) archives to Debian archives (.deb) archives using 7-zip itself, the resulting .deb file won't be valid Debian installation package, unless the 7-zip archive contained files in the exact proper structure for Debian.
Of course, you may also encounter situations where a Debian archive is further compressed using 7-zip, in this case you only need to just decompress the file to get your .deb archive.