This gist shows how to convert bytes input into an uint output. Then we can retrieve the bytes input by converting the uint value into an hexadecimal string

hex-to-uint-uint-to-hex-string.sol

//SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.5.0 <0.9.0;

import "@openzeppelin/contracts/utils/Strings.sol";


contract Test {
    
    uint256 public value;
    using Strings for uint256;
    

    function hexToUint(bytes32 _value) public {
        value = uint256(_value);
    }

    function uintToHexString() public view returns(string memory) {
        return value.toHexString();
    }

}