You need a PBO decryptor for that,
You can find one in the editors depot, Amalfi's PBO decryptor 1.5 is what you want!
You can select any PBO you like and UNPBO it, in case of a campaign, it will turn the PBO into a nice campaing folder in which you can find all the mission folders. Put these in your
Users/yourname/missions folder to use them in the editor.