Adding custom code to product page and checkout page

Hi! I'd like to add the code below to each product page's header and at the checkout page so I can track conversions from Mailchimp. Normally I go into the wheel of every page>advance and add the code there but I can't see where to do that in product pages or checkout. 

Thank you for your help!

<script id="mcjs">!function(c,h,i,m,p){m=c.createElement(h),p=c.getElementsByTagName(h)[0],m.async=1,m.src=i,p.parentNode.insertBefore(m,p)}(document,"script","https://chimpstatic.com/mcjs-connected/js/users/9fce44771f7d673adc52c2b87/cd709df9c2431ef7c5b608a10.js");</script>

Although I think this will work I can't be sure. I'm not all that familiar with MC.

Add the following to Store Settings > Advanced > Page Header Code Injection for the store page.

<script>

  /*
  
    begin add Mailchimp tracker code to product detail pages
    
    Version    : 0.1d0
    
    SS Version : 7.0
    
    Template   : Brine ( Aria, Blend, Cacao, Clay, Fairfield, Feed, Foster,
                 Greenwich, Hatch, Heights, Hunter, Hyde, Impact, Jaunt, Juke,
                 Keene, Kin, Lincoln, Maple, Margot, Marta, Mentor, Mercer,
                 Miller, Mojave, Moksha, Motto, Nueva, Pedro, Pursuit, Rally,
                 Rover, Royce, Sofia, Sonora, Stella, Thorne, Vow, Wav, West )
                 
    By         : Thomas Creedon < http://www.tomsWeb.consulting/ >
    
    */
    
  ( ( ) => {
  
    if ( ! document.getElementsByClassName ( 'ProductItem' ).length ) return;
    
    let script = document.createElement ( 'script' );
    
    script.id = 'mcjs';
    
    script.innerHTML = '! function ( c, h, i, m, p ) {' +
    
      'm = c.createElement ( h ), ' +
      
      'p = c.getElementsByTagName ( h ) [ 0 ], ' +
      
      'm.async = 1, ' +
      
      'm.src = i, ' +
      
      'p.parentNode.insertBefore ( m, p )' +
      
      '}' +
      
      '( document, "script", "https://chimpstatic.com/mcjs-connected/js/users/9fce44771f7d673adc52c2b87/cd709df9c2431ef7c5b608a10.js" );';
      
    document.getElementsByTagName ( 'head' ) [ 0 ]
    
      .appendChild ( script );
      
    } ) ( );
    
  /* end add Mailchimp tracker code to product detail pages */
  
  </script>

It may be possible to just throw the script you provided into the same place. Although that may cause noise in your tracking as that may track the product grid, category pages, ect.

The checkout page can not be modified. It is a SS security feature. However you might be able to throw the script you provided into Settings > Advanced > Code Injection > ORDER CONFIRMATION PAGE.

Let us know how it goes.

Thank you!! I've added the code and I'll let you know 🙂