To find the required .pbo file, first head to your directory that has your arma install, something along the lines of (Drive letter):\SteamLibrary\steamapps\common\Arma 3

Now depending on what mission/scenario you want to extract you may need to test extracting different .pbo files, as I'm wanting the escape from stratis mission i'll need the missions_f.pbo, mission and scenario files are located in (Drive letter):\SteamLibrary\steamapps\common\Arma 3\Addons




















Now we've found and got the correct .pbo file for my use case we need some sort of software to extract the contents of the file.

To extract our missions_f.pbo we need software, the best results i've gotten are from using PBOmanager v.1.4 beta.

Link: https://silentwisher.com/downloads-v2/arma-3-downloads/pbo-manager-1-4-beta/

Install PBOmanager and complete the installation process. When done open the manager:
It should look like this:











Click on the green button at the top and import the required pbo, It should be extracted and you should see its file structure:











The .pbo file has been extracted and now we can bring the contents into the Eden Editor.

To import the files select the necessary files and copy them (ctrl c)











Now paste these into your profile's missions folder, located usually (Insert drive letter):\Users\(user)\Documents\Arma 3 - Other Profiles\(Insert Arma username)\missions




















Now open the Eden Editor and open the mission, located in the mission folder.










Load the mission and start editing, once done save it or upload it to the workshop.