Forms can be configured to use the Internal Database, which saves the data within Confluence. All replies to that form are then accessed from the list of Forms using the Responses link for that Form ID.
Create a Space
Select Forms Configurations
Click on "Add Form configuration"
Provide a unique Form ID & give description to configure a Form ID
Save your Form ID Configuration.
The new Form ID will appear in your list.
You can now use this Form ID in the Forms for Confluence macro.