The previous widget used in the themes will no longer work. You can generate a new widget from snapwidget.com. You'll have to register, but generating a widget is free.
Follow By Email (Subscribe) Widget
As Blogger will discontinue the "Follow By Email" widget on July 11, 2021, you should download your subscriber contacts and look into using another newsletter service (MailChimp, Flodesk, etc). You can get in touch by email (fearnedesign@gmail.com) if you'd like me to switch the sign up forms for you and customize the new one.
Configure the Popular Posts Widget
To select how many popular posts are displayed, do this:
1. Go to Layout -> open the "Popular Posts" widget.
2. Change the number from the drop-down menu next to "Display up to X posts".
3. Click on "Save".