How to show ticket number on JIRA from submission?

Pop-up is blocked by the administrators, but I was able to add exemption but still no luck  

The pop-up blocker is a false lead. That's why the exemption changed nothing. What Ollie is describing sits in the corner of the page, drawn by Jira itself. A blocker governs new windows a site tries to open, and that is a different mechanism from an element the page renders inside itself. So the exemption was unrelated, and the notification still not appearing tells you nothing yet. Look again for a small notification in the corner of the page itself, not a separate window.

One of the keys above has a typo. It sends you nowhere. JIRACLOUD-98607 does not resolve; the project key is JRACLOUD, so it's JRACLOUD-98607, "Display created issue key on form post-submission confirmation", Gathering Interest on 3 votes. The other one Tobi gave you is real as written: JRACLOUD-94094, Gathering Interest on 17 votes. If you are voting, that second one is where the weight already is.

Tobi's automation route is the thing that works today. Build the comment variant rather than the email: a rule on work item created, scoped to that form's request type, adding a comment that mentions the reporter, which gets them a notification carrying the key and a link straight to the item they raised. It lands in the same place they would look anyway, and it survives someone missing a corner notification entirely.

unfortunately there is nothing showing up, I kept watching all four corners for long enough.

Then you were never going to find it, and I sent you looking. Sorry about that.

The corner notification Ollie described is the portal experience. If your requestors reach the form by its own URL instead, there's nothing to spot, because that path doesn't show a key at all. JRACLOUD-98607 describes your screen almost word for word: when a form is "accessed via direct URL", "the confirmation screen only displays a generic message: 'We're on it! Thanks for your response.'" and "There is no option to display the created issue key". So the blocker was a false lead, and so were the corners.

Which one you're on decides everything else here. The ticket names the shape it covers as a form reached at /jira/software/c/projects/PROJ/form/10044, so if that's the URL your requestors open, stop hunting for the notification.

Both tickets are open and neither has moved: 98607 is Gathering Interest on 3 votes, and 94094, the one Tobi linked, is Gathering Interest on 18 and was touched today. Worth a vote on 94094 rather than 98607 if you only bother with one, since it carries six times the interest.

That leaves Tobi's automation as the actual answer rather than a workaround. A rule triggered on work item created, scoped to that project and narrowed to what the form actually creates, emailing the reporter with the key, gets them the reference number the form won't give them. It arrives a moment later than a confirmation screen would, which is the only thing you lose.