Can I merge forms?

I have been using a particular form for 8 months.   We have a lot of good data on our reports.   I now want to upgrade my form to make it more robust.   I'm concerned I will now have two separate reports.   In other words, The data from my old form will be accessible through a link and the new form via another link.

Thoughts on how to approach this?

If you are editing the same form, the newly added fields will not be displaying any data for the old submissions. However, if there are any fields removed from the form, the existing data of the respective fields will be removed. 

If you want to clone the form to a separate form and edit it, the new data received on this form will be displaying all the information. That means you'll be having two forms and separate submissions. The existing submissions can be imported to the new form by using the Import submissions app. Please refer to the guide below that can help you with importing data.

https://www.jotform.com/help/308-Import-App-Easily-import-your-Excel-or-CSV-data-into-JotForm

Hope this information helps! Let us know if you are referring something different. We will be happy to assist.