From a quick glance at the latest Iowa Code 724, it appears you may have to take the course here. I dont know what kind of access you had to classes for the certificate in MA, but you have quite a few choices. Any web search will lead you to a number of reputable organizations that hold classes. There are also online classes for around $30. Ive posted those below for you.
Please take the time to read Iowa Code 724. It is the firearm laws for this state. If you have any questions, let us know.