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contracts...ExtraStorage.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.8; // Hi I'am new to Solidity

import "./SimpleStorage.sol";

contract ExtraStorage is SimpleStorage{
    // + 5
    // override
    //virtual override
    function store (uint256 _favouriteNumber)  public override {
        favouriteNumber = _favouriteNumber + 5;
    }
}

contracts...SimpleStorage.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.8; // Hi I'am new to Solidity

contract SimpleStorage {
    uint256 favouriteNumber;

    mapping (string => uint256) public nameToFavouriteNumber;
    
    struct People {
        string name;
        uint256 favouriteNumber;
    }

    // People[3] public peoples; you can give a fixed size
    People[] public peoples;

    function store(uint256 _favouriteNumber) public virtual{
        favouriteNumber = _favouriteNumber;
    }
    function retrieve() public view returns(uint256){
        return favouriteNumber;
    }

    function addPerson(string memory _name, uint256 _favouriteNumber) public {
        peoples.push(People({name:_name, favouriteNumber:_favouriteNumber}));
        nameToFavouriteNumber[_name]=_favouriteNumber;
    }
}

contracts...StorageFactory.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.8; // Hi I'am new to Solidity

import "./SimpleStorage.sol";

contract StorageFactory{

SimpleStorage[] public simpleStorageArray;

    function createSimpleStorageContract() public {
        simpleStorageArray.push(new SimpleStorage());
    }

    function sfStore(uint256 _simplestorageIndex, uint256 _simpleStorageNumber) public{
        //Address
        // ABI - Application Binary Interface
        return SimpleStorage(simpleStorageArray[_simplestorageIndex]).store(_simpleStorageNumber);
    }

    function sfGet(uint256 _simplestorageIndex) public view returns(uint256){
        return SimpleStorage(simpleStorageArray[_simplestorageIndex]).retrieve();
    }
}