How to convert USD amounts to ETH for transactions in my Ethereum dApp?

I am building a dApp where supermarkets send Ethereum tokens to customers as change after purchases. I want to make my frontend user-friendly by allowing users to input amounts in USD instead of ETH.

Here is my code for sending ETH to customers for my smart contract:

function sendMoneyToCustomer(address payable customer) public payable  { 
    balances[customer] += msg.value;
    customer.transfer(msg.value);
}


and this is code where I interact with the smart contract 

async sendMoneyToCustomer(signer, customerAddress, amount) {
    const contract = new ethers.Contract(this.contractAddress, this.abi, signer);
    const ethValue = ethers.parseEther(amount);
    const tx = await contract.sendMoneyToCustomer(customerAddress, { value: ethValue });
    await tx.wait();
}

I would like guidance on how to:

1. Fetch the current ETH to USD exchange rate.

2. Convert a user-provided USD amount to ETH before sending it.

3. Display user balances in USD instead of ETH.

Any help or code snippets would be appreciated!