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-v0.8.4+commit.c7e474f2.js&optimize=false&runs=200&gist=

contracts...DexScanner.sol

import "contracts/IUniswapV2Factory.sol";
import "contracts/IUniswapV2Pair.sol";
import "contracts/IERC20.sol";

contract DexScanner {

    struct Reserves {
        string symbol;
        uint112 reserve0;
        uint112 reserve1;
    }
    
    constructor() public {}
    
    function scanAllReserves(address factoryAddress) public view returns (Reserves[] memory){
        IUniswapV2Factory factory = IUniswapV2Factory(factoryAddress);
        
        uint256 pairsLength = factory.allPairsLength();
        
        Reserves[] memory reserves = new Reserves[](pairsLength);
        
        for (uint256 i = 0; i < pairsLength; i++) {
            IUniswapV2Pair pair = IUniswapV2Pair(factory.allPairs(i));
            
            (uint112 reserve0, uint112 reserve1,) = pair.getReserves();
            
            (address token0address, address token1address) = (pair.token0(), pair.token1());
            
            string memory token0symbol;
            string memory token1symbol;
            
            try IERC20(token0address).symbol() returns (string memory symbol0) {
                token0symbol = symbol0;
            } catch {
                token0symbol = "X";
            }
            
            try IERC20(token1address).symbol() returns (string memory symbol1) {
                token1symbol = symbol1;
            } catch {
                token1symbol = "X";
            }
            
            string memory pairSymbol = append(token0symbol, token1symbol, "-");

            reserves[i] = Reserves(pairSymbol, reserve0, reserve1);
        }
        
        return reserves;
    }
    
    function append(string memory a, string memory b, string memory delimiter) internal pure returns (string memory) {
        return string(abi.encodePacked(a, delimiter, b));
    }
}