I had a misconception that doing lots of abdominal exercises/crunches helps to reduce belly fat. I want to bulk up at the moment, for which I believe I have to follow a calorie surplus diet. But, If I am not mistaken, doing cardio along with following a calorie deficit diet helps to reduce belly fat as well as overall body fat at a faster rate. Now, my question is how to reduce belly fat and bulk up at the same time by following a calorie surplus diet?
First of all
Kudos for learning about the misconception, and adapting your approach.
You're also going to have to tweak your question from "how to reduce belly fat" to "how to reduce fat", because as you now know, you will either lose fat all over your body, or not at all.
Gaining muscle while losing fat
That's the holy grail of fitness. The truth of it is that it is entirely possible, but it can be very difficult.
In order to bulk up, yes, you're going to need a caloric surplus. But a bulk is meant for you to gain both muscle AND fat, and is traditionally followed by a cutting phase, whereby you diet down the fat you gained during the bulk.
What you're looking for is essentially a lean bulk, where you both gain muscle, and lose fat at the same time.
Let me just say this early; you're going to need to carefully study your diet in order to accomplish this. Fitness is the trifecta of training, eating, and resting. And the eating part is the most important one when it comes to gaining/losing weight.
Unfortunately, we can't tell you exactly how to go about it, because there is no training/eating plan that will work for everyone. It's something you're going to have to learn by trial and error, until you find that sweet spot where you're eating enough to gain muscle, but not so much that you gain fat.
You need to start out with any reasonable diet, and weigh yourself every morning after you poop. (That's where you get the best measurement because it's always going to be the same-ish amount of time since your previous meal.)
Follow this for a month, and keep measuring your weight, and looking at your progress in the mirror. Take pictures if possible, because the difference will be more visiblee when you can look at a month's progress side-by-side.
If you find that you're going in the right direction, then yay! Otherwise, if you're staying put, take a close look at your diet, and see if you can cut down on the calories. Preferably not by removing meals, but by substituting ingredients into something more healthy.
And don't necessarily switch it out completely. For instance, if you eat a lot of rice, that could be a high-calorie side-dish, but it's still good food. Try switching it out with a broccoli/cauliflower mix every other time you'd normally eat rice. Small changes are easier to cope with in the long run.
Then keep measuring your progress until you find what works. Eventually, you'll find that sweet spot.