Ultimate solution:
We assume that you already saved your project in a new folder but the audio and project folder are still at the old location
Step 1:
Save and close the project. Rename the new project folder to something slightly different, doesn’t matter what.
Step 2:
Open the project from the new folder again. It’ll ask you to assign a new project folder. Select the one you want to be the actual project folder.
Step 3:
Save and close the project. Move the audio files from the old folder to the new one (where you first need to create an ‘Audio’ folder). Or copy them over there. It’s just important that the ones in the old folder aren’t there anymore.
Step 4: Re-open your project. It’ll be like “??? where da files man” and then you can select your new audio folder with the ‘Folder’ button.
After that you just change the name of your new folder back to the actual one and you’re fine. 
Hope it helps!