Like this

document.querySelectorAll("img").forEach(img => {
  const url = new URL(img.src);
  if (url.searchParams.get("format")) {
    url.searchParams.set("format", "2500w")
    console.log(url.toString())
    img.src = url.toString()
  }  
})

<img src="bla.jpg?format=250w">
<img src="bla.jpg">
<img src="bla.jpg?format=350w">

Using Javascript:

Change the src property of the image:

function changeImage(){
document.getElementById('test-image').src = "https://url-to-second-image.com/image.png";
}

You can call the function using the click event in the html:

    <img id="test-image" src="the-url/first_image.jpg" onclick="changeImage()">

Here is a jsfiddle: https://jsfiddle.net/f5mwext3/2/

The same way you can change only part of the name (I'm using whole external files for convenience)