Just convert to CPython3. The 2->3 button at the bottom of your python script.
IronPython is on its way out , so might as well get started on conversion. Odds are there is nothing else that needs to be changed. There is some difference in how ILists are handled, but there are other posts here that describe those changes. The good news is there should be much better .Net integration in the future.
Outdated python engine - Developers - Dynamo (dynamobim.com)