Hi Lenova27,
This has to be one of the top 20 requests in this forum. I just answered a post yesterday regarding it. Bottom line is that you can't do it because you can't ensure that another person isn't submitting at the same time. You could do a two submit solution. Submit once, but don't close the form. Then, use a SharePoint list adapter to query the list, find the one you submitted, read the ID column and set that into your form. That works, but requires a double submit. Another option is to just use a GUID (global unique identifier) for your files name and incident number but they are long strings of characters and numbers and not very "friendly" to users. I'd go with the double submit for now. Will require adding a couple submits, a ShP data connection, and some rules to your form. Plus, when the list gets long, you will have performance issues when you filter the list to get the correct ID (you'll need to filter using a unique identifier - try using a date time stamp for now).
We've done this before. It would take about an hour to setup. If you want us to help you, we can do it, but you'll need to purchase a "Support Pack". Go to Qdabra.com -> Products -> Support - if you are interested. Otherwise, go for it. We'll be here to answer questions in the forum as they arise.