ARK: Survival Evolved

There are 2 ways of getting this achievement.

1st way is getting them legit (finding cords and those notes). https://ark.fandom.com/wiki/Explorer_Map_(The_Island)

2nd way is using dev console in a singleplayer game. For that just in the settings of host/local game make sure that "Admin logging" is turned on before creating a world.
Then after you've done that simply create a character and press "TAB" on your keyboard and enter this command "GiveAllExplorerNotes" (You can copy this command and paste it in console). After you've done so press "ENTER" to get those achievements.

This guide assumes you are playing with:

• Difficulty 5
  -- Wild creature levels increment in fives and wild creature max level is 150.
• "Singleplayer Settings" = Disabled
  -- Tamed creatures are MUCH stronger with it enabled but this guide is for the majority of the community who play on online servers.
• Map: The Island
  -- Not to be confused with Lost Island.

How to unlock the achievement: Defeat any difficulty of the Broodmother Lysrix.
How to defeat the Broodmother Lysrix on its easiest difficulty (Gamma):

Gather the three artifacts as tribute:

• Artifact of the Clever found in the central cave (Coordinates: 41.5 Lat, 47.1 Lon).
• Artifact of the Hunter found in the lower south cave (Coordinates: 80.2 Lat, 53.5 Lon).
• Artifact of the Massive found in the lava cave (Coordinates: 70.5 Lat, 86 Lon).

Now that you have the aritfacts you can summon the Broodmother Lysrix.
In singleplayer, you can only summon the Broodmother Lysrix at the green obelisk (Coordinates: 58.9 Lat, 72.3 Lon).
In multiplayer, you can summon any of the bosses at any supply crate or obelisk.

But hold on! You can't go in unprepared.
I suggest taming any megatherium at about wild level 130+ or above. Tame them using giant bee honey or kibble ideally.
Note: Megatherium are OMNIVORES meaning they will eat berries, vegetables, honey, meat, fish or kibble.
Use this taming calculator to find how much of each kibble or honey you will need: https://www.dododex.com/taming/megatherium

You should also tame a yutyrannus as when you use their alternate attack (use the C key) they will do an encouragement roar that boosts attack and defense. After the intial encouragement stay out of the fight and use this whenever a yellow ring appears above your creatures heads.
Tame any level of this but ideally a level 100+.
Note: Yutyrannus are CARNIVORES meaning they will only eat meat, fish or kibble.
Use this taming calculator to find how much of each kibble or honey you will need: https://www.dododex.com/taming/yutyrannus

Once you get two high level megatherium of opposite gender, you should breed them together until you have 19 of them. Saddle them up and bring them to the place where you will be summoning the portal to the broodmother arena alongside your yutyrannus.
Tip: Use a cryopod to transport your creatures in your pocket, like a pokéball.

Now encircle the supply crate or obelisk terminal with your creatures, put the tributes in and craft the portal. Once done, a dome will appear and give you about 30 seconds to adjust creatures not in the circle. Once 30 seconds is up, any creature that is not a flyer, climber or too big will be teleported to the arena with you.
Make sure your creatures aggression is set to neutral or attack my target.

The boss fight itself is relatively easy. Whistle your creatures to the behind of the Broodmother Lysrix with the comma key to wait for it to spawn its minions, araneos. Once the megatherium kill an araneo they will recieve the "Insect Killer" buff which GREATLY improves their attack and defense. Now whistle them to attack the Broodmother Lysrix with the period key. Make sure they encircle the Broodmother so theres not a few being blocked from attacking by other megatherium. Now the Broodmother should be killed very quickly.
If successful, the achievement should pop up! Don't forget your in game reward either! If not already auto-collected by one of your megatherium, there will be an end game resource called element and a trophy head in the Broodmother's inventory.

So if you're willing to do those achievements pretty fast (~30 minutes). Then you can use this guide and video:

Video:
Guide: https://www.reddit.com/r/Maka91Productions/comments/fcevy1/ark_survival_evolved_console_commands_text_used/

Or you can always do it legit (non console commands way) which will take you a lot of time.