Created using remix-ide: Realtime Ethereum Contract Compiler and Runtime. Load this file by pasting this gists URL or ID at https://remix.ethereum.org/#version=soljson-v0.8.7+commit.e28d00a7.js&optimize=false&runs=200&gist=

contracts...StorageFactory.sol

// SPDX-License-Identifier: MIT
pragma solidity >=0.6.0 <0.9.0;
import "./SimpleStorage.sol";

contract StorageFactory {
    
    SimpleStorage[] public simpleStorages;
    
    function createSimpleStorageContract() public {
        SimpleStorage simpleStorage = new SimpleStorage();
        simpleStorages.push(simpleStorage);
    }
    
    function sfStore(uint256 _storageIndex, uint256 _storageNumber) public {
        SimpleStorage simpleStorage = SimpleStorage(address(simpleStorages[_storageIndex]));
        simpleStorage.store(_storageNumber);
    }
    
    function sfGet(uint256 _storageIndex) public view returns (uint256) {
        return SimpleStorage(address(simpleStorages[_storageIndex])).retrieve(_storageIndex);
    }
}