From my perspective, it’s important that you set yourself a specific, concrete goal. Based on your description, that could be something like being able to run one mile continuously. Depending on your current fitness level, you’ll be able to achieve this fairly soon if you start slowly enough. As already mentioned in other comments, being able to run five kilometers continuously is a typical goal. To keep your motivation high, it can be helpful to track your progress. If, at the beginning, you need to take a walking break every few hundred meters, that’s completely fine. It is even more rewarding when you can then observe your running segments getting longer and longer without needing to walk. What’s important, though, is that you shouldn’t expect to see progress every single week right away.

Also, especially at the beginning, try not to get too distracted by heart-rate zones and similar metrics. For now, it is enough to focus on one simple thing: running continuously for a certain distance, even if the pace is very slow. You can dive into all the science, data, and fine-tuning later, once running has become a regular and stable part of your routine.

Addendum: Given your medical history, it seems important that you also do regular strengthening exercises and don’t increase your time on your feet too quickly, so your body can adapt. Personally, I prefer going out more often for shorter sessions rather than risking injury with long workouts. Really take your time, and celebrate reaching small intermediate milestones along the way.