Retrieving Ethereum Transaction Data using Javascript

From my website, I am trying to retrieve the transaction data stored on the Ethereum blockchain using Javascript.
Rinkeby Transaction Hash (Txhash) Details | Etherscan
If you see the transaction link in the Rinkerby test network, (click to see more) and then Decode the input, the data is hidden and needs to be decoded.
This is the data - which is a hash value, which I would like to retrieve: 6538482db543dedf2b2c2dd986ce475aa2732e24390534c729f749005035e073

I am using the Javascript fetch you retrieve the entire html page. But if I search the resulting htmlString - the data (hash value) is not there. I am not sure how the decoding happens and what piece of data needs to be decoded.

Any assistance on how to get the data (hash value) would be appreciated.

 <script src=""></script>
    async function FetchHtml() 
      let response = await fetch('');
      return await response.text(); // Returns it as Promise

    // Using the HTML
    async function Do()
          let htmlString = await FetchHtml().then(text => {return text}); 
	  let position ="div id="inputDecode");
	  console.log('position: ' + position)
	  var pos = htmlString.substring(
									position, position + 2000


<p id="demo"></p>
<input type="button" value="GetTransactionData" id="myCheck" onmouseover="Do()">