Google-sheets – Conditional Find and Replace in Google Sheets

If you highlight the column & press Ctrl-H you should be able to replace the string MKE how you want.

Before:

After:

Edit:
To auto fire this replacement:

In your sheet choose Tools|Script Editor from the menu & paste the code below which act on cells c1 to c10 on the sheet. The OnOpen method should fire when the sheet is opened, or can be fired directly from the script editor. I've not changed the UI to add the function to the menu, but that is also possible.

function onOpen() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var range = sheet.getRange("c1:c10");
  var to_replace = "MKE";
  var replace_with = "Milwaukee, WI";
  replaceInSheet(sheet,range, to_replace, replace_with);
}

function replaceInSheet(sheet, range, to_replace, replace_with) {
  //Confirm
  var ui = SpreadsheetApp.getUi(); 
  var spread = SpreadsheetApp.getActiveSpreadsheet();

  var result = ui.alert(
     "Will update " + to_replace + " to " + replace_with + " ",
     'Are you sure you want to continue?',
      ui.ButtonSet.YES_NO);

  // Process the user's response.
  if (result == ui.Button.YES) {

    // User clicked "Yes".
    spread.toast("Will update " + to_replace + " to " + replace_with + " ", "ALERT");

    var data  = range.getValues();

    var oldValue="";
    var newValue="";
    var cellsChanged = 0;

    for (var row=0; row<data.length; row++) {
      for (var item=0; item<data[row].length; item++) {
        oldValue = data[row][item];
        newValue = data[row][item].replace(to_replace, replace_with);
        if (oldValue!=newValue)
        {
          cellsChanged++;
          data[row][item] = newValue;
        }
      }
    }
    range.setValues(data);
    spread.toast(cellsChanged + " cells changed", "STATUS");
  }
  else {
    // User clicked "No" or X in the title bar.
    spread.toast("No action taken", "ABANDONED");
  }
}

Changing if (a>=find) vlst[i][j]=repl; to vlst[i][j] = a.replace(find, repl); replaces the first occurance of find in each cell.

The linked documentation discusses more advanced ways to use String.replace() such as ignoring case.

https://www.w3schools.com/jsref/jsref_replace.asp