Splinter Cell Blacklist Special Missions HQ is unlocked after Sam is rescued by Briggs from Sadiqs trap in Abandoned Mill.
US believes Iran is behind the Blacklist attacks, hence Sam decides to go on a risky mission and infiltrate the Qods Force HQ in Tehran to extract the data they have about the Blacklist.
The Splinter Cell Blacklist collectables in mission 6 can be easily acquired if you follow the collectibles guide in the same order as below.
Mission Description
INFILTRATE QODS FORCE HQ AND RETRIEVE INTEL ON THEIR CONNECTION TO THE BLACKLIST
Splinter Cell Blacklist Special Missions HQ Collectibles
Dead Drop Flash Drive
First you need to find your route into the Qods HQ by following the general. He leads you into an ambush, so dodge your enemies quickly and get in the next area.
Then you need to use a guards RFID chip to get inside the elevator and reach the vault. Get inside the vault and head to the control room thats on the other side of the area.
There is guard that checks this room after a while, so grab the Splinter Cell Blacklist Dead Drop collectible thats on the desk before he sees you.

Blacklist Laptop
After you have the drive you need to smash the window and use the fast rope. Evade the enemies while descending into the facility and you should open a door and reach a checkpoint. Theres a surveillance room in the next area and inside is the Blacklist Laptop.
You have to go stealth in order to avoid the destruction of the laptop. You can either sneak around the enemies from floor level or you can use the catwalks, but be aware that there are troops that use night vision goggles and they can spot you.

High Value Target
Near the end of the mission you have to escape through a garden. There are three guards patrolling in the first section of the garden, but they are easy to avoid.
Behind the wall that delimits the garden is the High Value Target. You can wait next to a bench for him to come to you and thus avoid any conflict with the remaining guards that are in the next section of the garden.
