How can i redirect a user to the PCP link once they login
You wont be able to redirect back to the thank you page, as the thank you page URL is dynamic (with _qfkey, etc.)

Alternative solution:

You can use the URL of the create personal campaign page as the destination after login.

In the href for the login page, you can use the below

please go &lt;a href="/user?destination=%2Fcivicrm%2Fcontribute%2Fcampaign%3Faction%3Dadd%26reset%3D1%26pageId%3D1%26component%3Dcontribute"&gt;here&lt;a&gt; to login


Note: The value for 'destination' query paramater should be encoded for the redirect to work correctly for any CiviCRM URLs.

So after login, the user will be redirected to the create personal campaign page directly. This will also avoid an extra button click in the user journey you are expecting (i.e after login redirect back to thankyou page and then the user click 'Create personal campaign page' button which then takes the user to create personal campaign page.

Hope this helps.