I did save my whole old GnuPG folder when I backed up stuff, though I don't think I have the proper keys to import into GPA.
The public and private keys are stored in the storage keyring namely pubring.gpg for public keys and secring.gpg for private keys.
If you have those, you can import them. Don't overwrite the file that exists on your new installation. In fact, in the directory from the old computer, rename the files secring.gpg --> secring-bak.gpg and pubring.gpg ---> pubring-bak.gpg
Then:
gpg --import pubring-bak.gpg
gpg --import secring-bak.gpg