Generate BaseURI and bulk upload NFTs - https://www.youtube.com/watch?v=GU2ZHXbrt90

BASENFT.sol

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.15;

import "erc721a/contracts/ERC721A.sol";

contract BASENFT is ERC721A {
    constructor() ERC721A("BASE URI NFT", "BUN") {}

    function mint(uint256 quantity) external payable {
        // `_mint`'s second argument now takes in a `quantity`, not a `tokenId`.
        _mint(msg.sender, quantity);
    }

    function _baseURI() override internal view virtual returns (string memory) {
        return "ipfs://bafybeifgxh2lo3jpx6xg2bl3wlnifgpahcdvmktl42jz7d7m7x7y6yap3i/";
    }
}

metadata_generator.js

var fs = require('fs');

for (var i = 0; i < 27; i++) {
  var json = {}
  json.name = "Token #" + i;
  json.description = "This is the description for token #" + i;
  json.image = "ipfs://CHANGE TO YOUR IMAGES CID/" + i + ".png";

  fs.writeFileSync('' + i, JSON.stringify(json));
}