To change the text of the unsubscribe link, change the shortcode in your email footer from {{ unsubscribe_link }} to:
{{ unsubscribe_link | replace_inner_html: "Your new text goes here" }}
To change the link text for the confirmation link change the shortcode in your confirmation email from {{ confirmation_link }} to:
{{ confirmation_link | replace_inner_html: "Your new text goes here" }}
Then replace the filler text between the quotes with your modified wording for the link.
If you copy the code directly from this page make sure to change the quotes in all parts of the code to normal straight quotes from left and right quotes or else the code will not work properly.