In order to transport your save file, you will need to create folders on your USB device while it's plugged into your PC.
Please use the following steps in order to complete this action;
- Whilst plugged into your PC, open your USB device and create a new folder named PS3.
- Create another folder inside the PS3 folder and name it SAVEDATA.
- Turn on your PS3 and plug your USB stick into the USB slot.
- Whilst on the XMB, go to Game > Saved Data Utility.
- Select your Far Cry 3 save data, press triangle and select COPY. You will then be prompted to select your USB device and complete the action.
-You can now delete the Far Cry 3 save data off your Playstation 3.
This should help avoid data corruption for your Far Cry 4 save data.