Unable to open tar.gz

[miner]

I am new to Ubuntu and am unable to open the Thunderbird.tar.gz file.

At the terminal I enter; tar -xvfz thunderbird-2.0.0.6.tar.gz

The response is;
tar z: cannot open: no such file in directory
tar: error not recoverable: exiting now

I have tried multiple times without success; printing "sudo" at the beginning of the command did not help. Leaving out the "z" or "gz" did not help. The file is on my desktop and I copied the path and inserted it into the command which also did not make any difference.

Also unable to open a tar.bz2 file. I entered "tar jxvf <filename>.tar.bz2

What am I doing wrong?
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