If what you want is the packages you have previously installed to your system so that you can install them again to the new one, this is one situation where it is probably quicker and easier to use the terminal to copy what you want from your filesystem to a usb disk with command
, and then copy them back to the filesystem of your new installation with
cp /var/cache/apt/archives/*.deb /media/path/to/usb
This is something I have done a lot and continue to do when necessary as it can save a lot of time downloading masses of packages that you have already in /var/cache.
sudo cp /media/path/to/usb/*.deb /var/cache/apt/archives/