How to migrate Tomboy Notes from a previous installation?

Firstly you should set the synchronization options of tomboy choosing synchronize to local folder.

Then store your the folder with removable hardware (you can also synchronize to dropbox). Set the tomboy synchronization path again after you reinstall your system to restore your notes.

I've done it before.

One thing I would recommend you don't do is copy the .note files over from one system to another.

I would use a different sync method (ssh sync for example) to get the notes synced to a new machine.

http://techno-geeks.org/2010/03/syncing-tomboy-notes-over-ssh/

Tomboy notes are stored in ~/.local/share/tomboy/. So just copy them!