JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="output"></ul>

JavaScript

const animals = [{ species: 'Pets', list: ['Dog', 'Cat', 'Rabbit', 'Gerbil', 'Turtle', 'Canary'] }, { species: 'Wild', list: ['Bear', 'Lion', 'Deer', 'Tiger', 'Cougar', 'Elk', 'Beaver', 'Elephant', 'Rhino' ] }, { species: 'Marine', list: ['Shark', 'Salmon', 'Squid', 'Octopus', 'Jellyfish'] }];

const searchQuery = 'Shark';

function fishForSharks(animal) {
  return animal.list.includes(searchQuery);
}

function getKeyPositionFromValue(obj) {
  return Object.keys(obj.list).find(key => obj.list[key] === searchQuery);
}

function output(obj) {
  const output = document.querySelector('.output');

  output.innerHTML += `
  <li>
    The <strong>${obj.species}</strong> species 
    contains a ${searchQuery} at position: 
    ${getKeyPositionFromValue(obj)}
  </li>`;
}

animals.filter(fishForSharks).map(output);