You can unzip using gunzip:
gunzip foofile.tar.gz
...which leaves you with foofile.tar
OR
You can call tar with the -z option:
List files in gzipped tar file...
tar -tvzf foofile.tar.gz
Extract files in a gzipped tar file...
tar -xvzf foofile.tar.gz
Paul
This archive was generated by hypermail 2.1.3 : Fri Aug 01 2014 - 17:34:55 EDT