How to make HTML render line breaks in Asp.net

I am trying to build a code formatting tool. My script gets the whole body text from the server and isolates the code block. I have the code and I am trying to check if there is a semicolon symbol in the body of the text and insert a line break after that character but the problem seems to be that HTML recognizes the <br> tag so it breaks any line. I have also tried to use a StringBuilder to append that tag after the semicolon character but it’s not working. Below is my code

@if(code != string.Empty){
//create a new instance of StringBuilder 
var str = new StringBuilder();
  //find where there is a semicolon
  foreach(var c in code){ 
    str.Append(c);
    if(c==';'){
        //append a line break
        str.Append("<br>");
     }
  }
  //display the code in the code div
  <p style="text-align:justify;">@str</p>
}

I also tried this

str.AppendLine();

which works when you write to the console but the HTML does not recognize ‘n’ as a new line character, it does recognize <br> instead, how do I make this work?