If you use a commercial VPN service provider, it might be easier and better for you to just install Tunnelblick on the new computer and get new configrurations from your provider and install them.
But if you can't do that or don't want to, and you have a fairly modern version of Tunnelblick, you can export the settings and configurations on your old computer and import them on the new computer. Important: usernames, passwords, and passphrases that you have saved in the Keychain ARE NOT exported or imported.
I strongly suggest that you make sure the configurations still work on the old computer first and make sure you know any usernames/passwords/passphrases needed to connect them.
Then export them to a file on the Desktop as described below, move them to the new computer. Install Tunnelblick on the new computer, and go through the Welcome dialog, click that you have configurations, click to acknowledge that you understand how to install them, and, then (finally) drag/drop the file onto the Tunnelblick icon in the menu bar.
To export the settings:
- Launch Tunnelblick
- Click on the Tunnelblick icon in the menu bar,
- Click "VPN Details"
- Click on the large "Utilities" button at the top of the window
- Click on "Export Tunnelblick Setup" button.
The file will be put on your Desktop. (Depending on your version of macOS, you may need to give Tunnelblick permission to access the Desktop.)