In the example code:

• Donate is the current button text. You need to change it to your current button text.
• new text is new button text. You can change it to new text
• Google.com is an example URL. You can change it to the URL that you want

One Page

#1. Enter this code in the Page Header Code Injection and click Save 

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.0/jquery.min.js"></script>
<script>
$(document).ready(function(){
    $("a.btn").html(function() { 
          return $(this).html().replace("Donate", "new text");  
    });
  $("a.btn").attr('href','https://google.com');
});
</script>

#2. You will have a result like this

Cart Page

#1. Add this code to Code Injection > Footer and click Save

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.0/jquery.min.js"></script>
<script>
$(document).ready(function(){
    $("body#cart a.btn").html(function() { 
          return $(this).html().replace("Donate", "new text");  
    });
  $("body#cart a.btn").attr('href','https://google.com');
});
</script>

 

#2. You will have a result like this

Paywall Page

#1. Add this code to Code Injection > Footer and click Save

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.7.0/jquery.min.js"></script>
<script>
$(document).ready(function(){
  $('#sqs-paywall-page-root').closest('body').addClass('paywall-body');
    $("body.paywall-body a.btn").html(function() { 
          return $(this).html().replace("Donate", "new text");  
    });
  $("body.paywall-body a.btn").attr('href','https://google.com');
});
</script>

#2. and result like this.