Use SyntaxHighlighter.
Just add following code before :

<link href='https://cdnjs.cloudflare.com/ajax/libs/SyntaxHighlighter/3.0.83/styles/shCore.min.css' rel='stylesheet' type='text/css'/>  
<link href="https://cdnjs.cloudflare.com/ajax/libs/SyntaxHighlighter/3.0.83/styles/shThemeDefault.min.css" rel="stylesheet" type="text/css" />  
<script src="https://cdnjs.cloudflare.com/ajax/libs/SyntaxHighlighter/3.0.83/scripts/shCore.min.js" type="text/javascript"></script>  
<script src="https://cdnjs.cloudflare.com/ajax/libs/SyntaxHighlighter/3.0.83/scripts/shAutoloader.min.js" type="text/javascript"></script> 

<script language='javascript'>//<![CDATA[  
window.onload = function(){  
  function syntaxHighlighterPath() { 
    var args = arguments, 
    result = []; 
    for(var i = 0; i < args.length; i++) { 
      result.push(args[i].replace('@', 'https://cdnjs.cloudflare.com/ajax/libs/SyntaxHighlighter/3.0.83/scripts/')); 
    } 
    return result 
  }; 

  SyntaxHighlighter.config.bloggerMode = true; 
  SyntaxHighlighter.autoloader.apply(null, syntaxHighlighterPath( 
    'applescript @shBrushAppleScript.min.js', 
    'actionscript3 as3 @shBrushAS3.min.js', 
    'bash shell @shBrushBash.min.js', 
    'coldfusion cf @shBrushColdFusion.min.js', 
    'cpp c @shBrushCpp.min.js', 
    'c# c-sharp csharp @shBrushCSharp.min.js', 
    'css @shBrushCss.min.js', 
    'delphi pascal @shBrushDelphi.min.js', 
    'diff patch pas @shBrushDiff.min.js', 
    'erl erlang @shBrushErlang.min.js', 
    'groovy @shBrushGroovy.min.js', 
    'java @shBrushJava.min.js', 
    'jfx javafx @shBrushJavaFX.min.js', 
    'js jscript javascript @shBrushJScript.min.js', 
    'perl pl @shBrushPerl.min.js', 
    'php @shBrushPhp.min.js', 
    'text plain @shBrushPlain.min.js', 
    'py python @shBrushPython.min.js', 
    'ruby rails ror rb @shBrushRuby.min.js', 
    'sass scss @shBrushSass.min.js', 
    'scala @shBrushScala.min.js', 
      'sql @shBrushSql.min.js', 
    'vb vbnet @shBrushVb.min.js', 
    'xml xhtml xslt html @shBrushXml.min.js'
  )); 

  SyntaxHighlighter.all(); 
} 
//]]></script> 

References: