The Legend of Zelda: Tears of the Kingdom has an incredibly large amount of quests for you to partake in. The Main quest line will see you overcoming several dungeons and facing incredibly fearsome foes. Not all quests will be as serious toned as the main quest line, there are a lot of light-hearted adventures to be had in the game too.
You will also get plenty of side quests to partake in. A lot of these side quests and adventures will see you interacting with one or more of the many natives of Hyrule to help them out with something troubling them. It is not uncommon for some side quests and side adventures to be part of others. You will find times you will need to complete a task at hand before you are able to resolve a different one.
Starting The Quest
Between Hateno and Retsam Forest Cave, there will be a stable. If you follow the trail between these two points, you will come across it, or you can look at the provided image above. Here you will find an NPC named Dantz. Dantz will give you the quest once you have finished speaking with them.
Where To Find Acorns
The acorns you seek can be gathered from Retsam Forest, which is East of the stables you are currently at. Head on over there. There are two ways of acquiring these Acorns. You can chop down trees for a chance to have some drops, or you can kill Squirrels. Squirrels are rather fast, so it is best you use your bow and hit them from a distance. It should not take long to get all the acorns you need from this location.
Completing The Quest
Return to Dantz at the stable where you first started the side quest and engage in dialog with them again. They will reward you with some Fresh Milk. At the end of the dialog, you will have completed the Quest.