Arrow length can be governed by several things, but to get to where you can answer this question, you will need to become proficient in tuning your bow and arrow shaft to each other.
You will need to understand the archers paradox, and how your riser is cut in relation to the center line. You will need to have an idea of your tip weight in relation to what you’re going to shoot at, (animal or target)
Understand the different shaft spines and how your bow reacts to them. Shooting style can also effect shaft length, for instants, gap shooter sometimes like a longer shaft, to give them a smaller gap.
There are so many elements to the equation that only YOU can determine what that correct length is. And if a person behind the counter tells you any different, then you will know your talking to the wrong person.
Start by learning to tune bare shafted.
My draw is 28.5, arrow length is 30.75. It took me 2 years before I found an arrow spine and length that me and my bow was really comfortable with.
This is just my humble opinion, I could be wrong.
Good luck on your journey!