Tic-Tac-Toe-3a.jsx

class Board extends React.Component {
  renderSquare(i) {
    return (
      <Square
        key={"square " + i}
        value={this.props.squares[i]}
        onClick={() => this.props.onClick(i)}
      />
    );
  }

  renderSquares(n) {
    let squares = [];
    for (let i = n; i < n + 3; i++) {
      squares.push(this.renderSquare(i));
    }
    return squares;
  }

  renderRows(i) {
    return <div className="board-row">{this.renderSquares(i)}</div>;
  }

  render() {
    return (
      <div>
        {this.renderRows(0)}
        {this.renderRows(3)}
        {this.renderRows(6)}
      </div>
    );
  }
}

The assignment was to have two for loops, I only see one in your solution.

I've changed renderRows() and render() to meet the requirements

renderRows(r){
      let rows = [];

      
      for (let i = 0; i < r; i++) {
        rows.push(<div className="board-row">{this.renderSquares(i*3)}</div>)
      }
      return rows;
    }

    render() {  
      return (
        <div>
          {this.renderRows(3)}
        </div>
      );
    }