Thank you pages and confirmation page URLs contain dynamic parameters specific to the user's session, so it is not possible to have a specific url for a thank you page that generates after a donation.

However, the sample URL below can provide some idea of what the URL would look like. Where XXXX is the donation form ID  and XXXXXXXX is the autogenerated value that will change for each user.

domain.com/shortname/site/Donation2?idb=XXXXXXXX&df_id=XXXX&XXXX.donation=completed&idb=XXXXXXXX