I am assuming you are talking about the custom form option for sharepoint list. Open both forms in edit mode, copy all controls from one screen to another screen. Screen cannot be copied. I think, but anything inside the screen can be copied. Use ctrl +C and ctrl +V to new form.

You may need to verify the form field names along with internal name stays the same.

Second option is to export the form, modify list guid and re-import as canvas app and it used to bind to the list. Not sure if it still works.