Hi @GIS_1234_KS
In Connect, you can customise the text that appears in the thank you screen in the web app using a note question with generated_note_prompt_submitted as the question name. This supports using question placeholders in the label (and also HTML), so for example the label for the question could read something like:
Thank you for taking part. Your URN is <font color="red">${urn}</font>.
You can also customise the text for the footer, submit button, and more. Please see the Rewrite UI elements documentation and the Survey123 Tricks of the Trade: Introducing Multilingual Surveys blog post for more details.
Hope this helps. Best, Jim