Korky Complete Toilet Repair Kit - Size: Large 3-Inch - Fixes: Running, Noisy, No/Slow Refill, and No/Weak Flush Toilets - Easy to Install, 5010MP

Yes replace bolts, the sets come with the bolts fyi. The 2 vs 3 inch refers to gasket(usually red in color) that sits under the tank and above the seat of the toilet. It is hard to see from the front but for most toilets you can see it if you look around. You need to look up your toilet make and model. Open the tank again and look inside. Sometimes it will tell you the model. The brand is usually somewhere on the toilet, I think outside the tank. Here is an example of a set, note this is 3in, which is uncommon. But the set includes everything except the handle. I would replace the handle as well, since you will be taking apart everything. https://www.amazon.com/Korky-3-inch-Complete-Toilet-Repair/dp/B0F8C7JGGS