I'd suggest you move your entire profile. https://support.mozilla.org/en-US/kb/profiles-where-thunderbird-stores-user-data You ''could'' pick out your address books from the profile. They are stored in files with .mab extensions but you'll have an interesting time of it working out which address book each represents, and importing it, if you have any user-defined address books. Personal Address Book is stored in abook.mab and Collected Addresses is stored in history.mab. These two files can be simply copied from one machine to another. User-defined address books are not so simple. Alternatively you could export the address books on the old computer and import them into the new. I'd recommend the LDIF option for this.