The other people are right that your body burns fat wherever it wants and that diet is fundamental, but there's something a lot of people miss: after 5 years without exercise, when you go back to the gym 3 times a week, it's normal to see changes in your arms and back first because those muscles respond faster to training. The belly is really the last area to get defined, and that can be demoralizing, but it doesn't mean nothing is happening. What you can do at the gym is put in more resistance work and intense cardio (sprints, burpees, things that get your heart racing) because that really does impact your overall calorie deficit more than just ab work.
The crucial thing is that you actually need to look at what you're eating. It's not just "fewer calories," it's what kind of food. If you eat a good breakfast, get protein at each meal, and cut out the ultra-processed stuff, you're going to see a difference without having to count every gram. At 34, your metabolism isn't what it was, yeah, but it's not destroyed either. What works better is combining things: 3 times at the gym is fine if you put in real intensity, plus more walking on other days (I go out in the mornings and it really makes a difference), and then the diet. Without the right diet, your abs are going to be strong but they're going to be under the fat, invisible.