You shouldn't use JSON.stringify. since it's already object

Just change it to below code

  const response = await axios.get('http://localhost:5000/api/products');
  setItems(response.data);

axios.get() method returns the object and you can't use the map() method on an object as it's been defined on the prototype of an array. You can find more details of Array.prototype.map() here

First of all, let's understand what axios.get() method returns.

{
  // `data` is the response that was provided by the server
  data: {},

  // `status` is the HTTP status code from the server response
  status: 200,

  // `statusText` is the HTTP status message from the server response
  statusText: 'OK',

  // `headers` the HTTP headers that the server responded with
  // All header names are lower cased and can be accessed using the bracket notation.
  // Example: `response.headers['content-type']`
  headers: {},

  // `config` is the config that was provided to `axios` for the request
  config: {},

  // `request` is the request that generated this response
  // It is the last ClientRequest instance in node.js (in redirects)
  // and an XMLHttpRequest instance in the browser
  request: {}
}

You can find more details here. That means the actual data you are looking for resides in response.data. You need to extract it.

const { data } = response;

Now you need to analyze and process the data into the React renderable format.

It worked by setItems(response.data)

import React from 'react'
import { useState } from 'react';
const axios = require('axios');

const Api = () => {

const [items, setItems] = useState([]);

   const getItems = async () => {
        try {
          const response = await axios.get('http://localhost:5000/api/products');
          console.log(response.data);
          
          setItems (response.data);
         
          console.log(response.data)
        } catch (error) {
          console.error(error);
        }
        
}

return (
    <div>
        <button onClick={getItems}> Fetch Data</button>
        <br />
        <br />
        <br />
       
        {items.map((item)=>(
            <div >
                <h1>{item.name}</h1>
                <h2>{item.price}</h2>
            </div>
        ))}


    </div>
)

}

export default Api