Dark Ops Challenge 7 is called “Respect your Elders” and requires you to pay respects to Tanbor Fudgely’s memorial.
The memorial for this Dark Ops Challenge is located on F6 in the Blackout map. On the north end of the bridge, you can find the memorial. Walk up to it and step on the last stone in front of the monument. Press X/Square while you stand on the stone to activate the bow animation for your character. After finishing the game you will be rewarded with the new “Respect your Elders” calling card in your Dark Ops Challenges.
The Blackout Mode in Call of Duty Black Ops 4 has 9 Dark Ops Challenges. None of them have a description or location attached until you find the actual challenge and complete it. Once you complete a dark ops challenge you unlock a new calling card.
-Credit to reddit user EvolV2