First, edit your Sweep3 and de-select "Merge result". That will create this Sweep as a separate body instead of blending it with the rest of the Part. Do the same for Boss-Extrude8 (at least I assume you want it mirrored also).
Next, you'll need to edit LPattern3. De-select "Features and Faces" and choose "Bodies" instead.
Now you'll be able to Mirror the bodies. Again, make sure you have "Bodies to Mirror" selected instead of "Features to Mirror".
First, edit your Sweep3 and de-select "Merge result". That will create this Sweep as a separate body instead of blending it with the rest of the Part. Do the same for Boss-Extrude8 (at least I assume you want it mirrored also).
Next, you'll need to edit LPattern3. De-select "Features and Faces" and choose "Bodies" instead.
Now you'll be able to Mirror the bodies. Again, make sure you have "Bodies to Mirror" selected instead of "Features to Mirror".