Hello and Welcome to LinuxQuestions,
It depends on what package manager/software center you use. If for example you use the apt-get command from the console then packages you've already downloaded will be saved in /var/cache/apt/archives. You could try to find out with the find command:
sudo find /var/cache -type f -name '*.deb'
Also change the title of your thread to something more descriptive. Just 'help me' isn't drawing any attention to your problem.