I was certified as a EMT-B and worked as an EMT-B about 13 years ago. I then had my national EMT-Paramedic certification but never worked as a paramedic. Do I need to do the entire EMT course again?

You do not have to do the entire EMT Course again, since the NREMT has a Re-Entry program. You can check that out here: https://www.nremt.org/Document/EMT-Re-entry-Pathway

If you decide to re-enter at EMT level you will need the 40 hour refresher that we offer here: https://www.impactems.com/course/emt-recertification-40-hour/?prod=40

Then you will need to retest the NREMT cognitive and psychomotor exam through your state EMS office.