This quest starts automatically on the Nexus, after you first meeting with the Initiative leadership. After Eos you’re able to have a chat with your sibling to advance things further, and following that your next goal is to visit planets and seek out Memory Triggers… which are scattered about for the sake of collectibles, or something. Anyways, below are the ones you can find on Voeld.

From the Forward Station near (south of) Hjara Station, drive south, southwest to find a Memory Trigger. This particular Memory Trigger is near a Mining Zone icon on your map, on a precipice overlooking the valley below.
Make your way a good distance east, southeast from Techiix Station to find this Memory Trigger, which is on a rather unimpressive hill south of a Kett structure (marked on your map as a “Point of Interest”).
On a hill overlooking the outpost site for Voeld (northeast of the map marker) you’ll find this Memory Trigger.
Log these three Memory Triggers on Voeld and you’ll be able to return to the SAM Node on the Hyperion and access another memory. Yep, another memory of mom, although one must wonder why you needed memory triggers to access this one, considering your character was involved in this memory. No good reason why you needed to trek all over Voeld for this. Oh well.