Find the Cache Quest is a part of Fallout 76 Key to the Past
Find the Cache Walkthrough
With all of the necessary items and information obtained, you can finally go to the cache located in Pleasant Valley Ski Resort, directly east of Top of the World. The area will likely be guarded by Mole Miners, so clear them out and head inside the resort. Head up the stairs behind the front desk then down the hall toward the gift shop. Take the stairs to your left down to the bottom floor where you will find a keycard locked door.
Rose will tell you to check for the key under the floormat in front of the laser guarded door. Grab it and head inside to complete the quest! There is some loot to grab inside the cache, as well as a level 3 lock safe you can open if you have the perk cards.
Next to the safe you will find the Broken Uplink, needed to continue The Missing Link main quest.
Congratulations! Key To the Past Mission is completed.