How calculate number of days between created date a custom date field?

[Shah Baloch]

How can I get the number of days between two date fields and add them to a custom field? For example, I have a custom date field "Issue Reported Date" and I will create another custom field "Number of days". I would like to get the number of days between the system field "created" and the custom field "Issue Reported Date". The Issue Report Date is always earlier than the issue-created date.  For example, the Reported date is 03/20/2022, and the Issue was created on 03/24/2022.  Here is another logic:

Issue Reported Date: 03/20/2022
Created: 03/24/2022
Number of days: 4

I would like to have the Number of days custom field on the view screen. I searched in the community and saw some posts but I couldn't understand how it works, not sure it can be a Behaviours script, listener, or something else.

I'll be thankful if someone can help me with this.