NFT.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract MyNFT is ERC721, Ownable {
    using Strings for uint256;

    // Base URI
    string private _baseURIextended;

    constructor(string memory name, string memory symbol) 
        ERC721(name, symbol) 
    {}

    function setBaseURI(string memory baseURI_) external onlyOwner {
        _baseURIextended = baseURI_;
    }

    function _baseURI() internal view virtual override returns (string memory) {
        return _baseURIextended;
    }

    // Function to set/update the URI of a specific token
    function setTokenURI(uint256 tokenId, string memory tokenURI) public onlyOwner {
        _setTokenURI(tokenId, tokenURI);
    }

    // Override function to return the full URI of a token
    function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
        require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");

        string memory base = _baseURI();
        return bytes(base).length > 0 ? string(abi.encodePacked(base, tokenId.toString())) : "";
    }
}