Hi @billweberg, we certainly advocate for repairing the poles instead of replacing; and hopefully this guide helps get your started:
[guide|174350|How to Replace the Tent Poles Elastic - iFixit Repair Guide|new_window=true]
If you don't have existing elastic to measure against, then it's worth cutting longer to start, and then cutting it shorter once you've made a first test. Take care to use a medium-strength elastic too, as too thin won't keep the poles together, and too strong will be difficult to assemble. Good luck! 💪🛠️