Your FTP logins are stored with your other saved passwords. This article describes the files that that store this data: Recover important data from an old profile. If you only need to move data in one direction, you could copy the two files and then drop them into your active settings (Firefox profile) folder on the second PC to replace the existing ones.

To easily access your active settings folder, use:

Help > Troubleshooting Information > "Show Folder" button

If you need to merge data between the two profiles, I don't know whether you can do that without an add-on. In theory Sync should do it, but... I'm not sure I trust Sync yet. Backups definitely would be recommended before trying it.

Sorry, I neglected to mention that the file fireFTPsites.dat has all the connection information other than the passwords.