Swimming, cycling, rowing (e.g., erg machine), and running are great cardio exercises! Running is probably the worst on that list because it is the most impact-heavy.
I don't have a program for you to follow for your needs, as I come from a competitive mid-distance and distance running background myself. In my adulthood I've transitioned to cycling due to impact-related injuries. Here's my advice when it comes to cardio, though:
Get a good heart rate sensor and moderate your efforts based on time and effort as expressed by heart rate. Ignore distance as much as you can. Keep your efforts below or well below your anaerobic threshold. Lots of formulas to use to calculate that, but generally speaking for a person my age and relative athletic ability, exceeding 150 BPM (beats per minute) is exerting myself too much when doing cardio. (There are specific and deliberate reasons you might exceed that threshold for endurance training, but I don't see how those fit with your current goals).
Hope that helps! I am not an expert, just speaking from personal experience and the few books I've read on endurance running.
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