first bare version

src/App.js

 import './App.css';
-import { Counter } from './Counter';
-import { default as Grid } from './Grid.js';
-
 const App = () => {
-  const compteurs = []
-  for (let pas = 0; pas < 5; pas++) {
-    compteurs.push(<Counter title={"Le compteur n° "+String(pas)}/>)
-  }
   return (
     <div>
       <div className="App">
@@ -14,9 +7,6 @@ const App = () => {
             <h1>Bienvenue sur notre super site !</h1>
           </div>
       </div>
-      <Grid>
-        {compteurs}
-      </Grid>
     </div>
   );
 }

src/Counter.js

-import { useState } from "react";
-
-const Counter = (props) => {
-    const [count, setCount] = useState(0);
-    return (
-        <div class="card" style={{width:"auto", margin: '2em'}}>
-            <div class="card-header">
-                {props.title}
-            </div>
-            <button
-                type="button"
-                class="btn btn-primary"
-                onClick={()=>setCount(count+1)}
-                style={{margin: "1em"}}
-            >
-                Ce bouton incrémente
-            </button>
-            <p style={{margin: "1em auto"}}>Là genre ça vaut {count}</p>
-        </div>
-    )
-};
-
-export { Counter };
\ No newline at end of file

src/Grid.js

-import './grid.css';
-
-const Grid = (props) => (
-    <div class="grid">
-        {props.children}
-    </div>
-)
-
-export default Grid
\ No newline at end of file

src/grid.css

-.grid {
-    display: grid;
-   grid-template-columns: repeat(3, 1fr);
- }
\ No newline at end of file