The library could not be opened because the file system of the library’s volume is unsupported.

We recommend to use "Mac OS Extended (Journaled)" on an external drive where you are going to store your Aperture library. Copy the library to the internal disk and open it from there. Then, use Disk Utility to format the external disk > http://pondini.org/OSX/DU1.html Copy all the files on the external drive to the internal disk before formatting.

Note that you will lose the ability to use the external disk with PCs, so you will need an application like Paragon HFS on all PCs you want to use the external disk

Is your library on a drive, that is not formatted Mac OS X Extended (Journaled)? Then the newer versions of Aperture cannot open it. Move the library to a drive that is formatted for MacOS.

You can check the format of the drive with Disk Utility and reformat the drive there. But reformatting will erase it, so you will need to copy the contents to a different drive before you do that.

See this document: Aperture: Use locally mounted Mac OS X Extended volumes for your Aperture library

Correct. You have FAT32, so if you want to use the Aperture library on the external drive, you will have to format it in Mac OS Extended. A different workaround is to copy the Aperture library to the internal disk

Good luck

As mende1 says. Only check, if you have enough free disk space left on your system drive, since you want to merge two Aperture libraries. Aperture will need more than twice the size of the merged library as working space during the merge.

and will buy a airport express tomorrow.. that will also solve my backup problem then if I keep it internal I hope...

A good plan!