[Ethereum] Project ID is required

I got an error at sendSignedTransaction is : Project ID is required.
Can you please let me know that what is the actual problem?

This is my code:

try {
    const ethereumUri = 'https://ropsten.infura.io/API_KEY'; //process.env.API_URL

    var web3 = new Web3(new Web3.providers.HttpProvider(ethereumUri));

    const keystore = web3.eth.accounts.encrypt(req.body.privateKey, 'Drc@1234');

    const privateKey = new Buffer.from(req.body.privateKey.substr(2), 'hex')

    const decryptedAccount = web3.eth.accounts.decrypt(keystore, 'Drc@1234');

    var amount = web3.utils.toWei(req.body.transaction_value.toString(), "ether");

    var fee_eth = req.body.transaction_fee * 1000000000;
    var convertTOGwei = fee_eth / 21000;
    var decimalLimit = convertTOGwei.toFixed(2);
    var fee = web3.utils.toWei(decimalLimit.toString(),'gwei'); 

    var sender = req.body.from_address;
    var receiver = req.body.to_address;

    /*var rawTransaction = {
        "from": sender,
        "to": receiver,
        "gasPrice": web3.utils.toHex(fee),
        "value": web3.utils.toHex(amount),
        "gas": 21000,
        "chainId": 3
    };*/

    const txCount = await web3.eth.getTransactionCount(sender)

    // Transaction
     const txObject = {
        nonce:    web3.utils.toHex(txCount),
        to:       receiver,
        value:    web3.utils.toHex(amount),
        gasLimit: web3.utils.toHex(21000),
        gasPrice: web3.utils.toHex(fee)
     }

    // Sign the transaction
    const tx = new Tx(txObject, { chain: 'ropsten', hardfork: 'istanbul' })
    const pk = Buffer.from(privateKey, 'hex')
    tx.sign(pk)

    const serializedTx = tx.serialize()
    const raw = '0x' + serializedTx.toString('hex')
     // Broadcast the transaction
    const receipt = await web3.eth.sendSignedTransaction(raw)
    return receipt;
} catch (e) {
    console.error(`try/catch Error:(${e})`);
}