If you go into raspi-config and make sure SSH is turned on, then you can use FileZilla to simply transfer files from one to the other. You can do this by installing FileZilla on the older unit and transfer to the new. Or, even better, use FileZilla from a PC and make a backup copy of your important files on your hard dive. Then use it to copy those files to the new one.
Or, you can use scp to copy files and directories individually directly between Pis.
I see the accepted answer and it is a good one, which will make an exact clone of the older system, using Win32DiskImager. The only gotcha is if you have assigned static IP addresses then they both would end up with the same address and you would want to deconflict those.
If you use that method you can begin with a blank SD card and skip the NOOBS installation altogether.