Replied on another thread - copying here for convenience
Form submissions can’t be copied from one project space to another. You could however, copy cases over. The easiest way to do that would be to do a data export of the cases you want to transfer, then import those cases into the new project space. You’ll want to be sure to assign the case owners correctly in this step, or using the “reassign cases” feature after, so the appropriate users have access to the cases on the new project space.