Right-click it in CM and select "List Dependencies recursively". You will want to make sure you get all the dependencies with it. Select all the dependencies. Right click the asset in CM and select "Export to CDP". Give it some name like "Brandon". If you have everything selected, it will export a CDP file with everything in it to your downloads folder or wherever you select. When you get your new install, you can just drag-and drop it into the new CM.
EDIT: Sorry, not sure if this works for packaged items. I am wondering if you should be able to go to the Content Store in your new install and download it from there? Or maybe check and see if it is in "My Trainz - My Digital Downloads"?