I don't agree that one needs to know how many calories one is absorbing or expending, or that one needs to count steps - but it is all good if that is what you are into! Just that it isn't necessary. I personally don't enjoy counting anything, so I didn't (until I wanted to particularly target my treatment with various ways of eating, which boringly have involved counting). Walking has been a hugely important part of my own treatment. I changed my way of eating, and walked, and lost 15-20kg in three or four months. My HBA1c went from 93 to 67 in that time, I think. I walked a lot! There are many in this forum, however, who have had much more dramatic HBA1c drops than mine. (Mine is now 43.) But I came to counting carbs rather late in the piece.
Walking is a great, variable, and enjoyable way to get your limbs moving and your muscles working, and I would let your own body determine how much, for how long - what feels good and good enough for you and your health as a diabetic.
But, saying that, the recommended amount I have read on many diabetes websites is at least a half hour five days a week. It sounds pretty reasonable to me, and can include things like walking around a supermarket, or mowing the lawn, walking to and from transport - that kind of thing. It can also improve mood hugely, and as it can be more than a bit stressful and worrying being diagnosed with a chronic health condition - and feeling happy is great for our health. I personally prefer to have somewhere to walk to, with a goal in mind, even if it is just getting to work, a cup of coffee at a cafe, or a particular shop or event or a friend's place, rather than take the car or public transport. It's amazing how much walking/steps you can clock up that way. Now one of the goal-places I walk to is an outdoor gym where I bench-press, but I wouldn't have been doing that soon after diagnosis!
Good to see the 30 mins at least five days a week as a baseline, from which you can increase? When you feel up to it, or want to, with your blood glucose levels (and your weight in your case) spurring you on? And the beauty of physical exercise is it gets easier and faster the more you do it.