Simply gather all 7 Dragon Balls from around the world map and summon Shenron for the 10th time. Note that this cannot be done during main sagas in the story and only during intermissions.
I waited till I finished the story to do most of mine and it takes 20 in-game minutes for them to restore and you will know when this has happened because Bulma will contact you to say they're available to collect.
This video shows me collecting them for the final time after Bulma contacts me.
I created this video to help:
Hope this helps.