Is there a way to set up a confirmation email for whenever someone submits one of our online forms? for example, if someone registers for one of our user groups, would we be able to automatically send them a confirmation email?
Yes, create a campaign that is triggered on form fill. Identify the form you specified above.
In the flow send an email.
There's also a handy step-by-step guide available if you need it: Email Auto-Response - Marketo Docs - Product Docs