I suggest using your own reasoning skills.
At night, when you look up in the sky, you see that the moon is round. In the daytime, you look up in the sky, and you see that the sun is round. If you buy, borrow, or use a telescope you can look at other planets in our solar system, and see for yourself... that they are all round. Likewise, you can plan a trip to visit a local observatory. Most Universities have observatories that allow the public to come, and do viewings with their telescopes at different times. You can call one near you, and get some information about it, and go on one of their events, so that you can see some of the planets in our solar system. You can see with your own eyes, that they are all round.
Then... think to yourself, why is it... that the Moon is round, the Sun is round, all the planets are round, and... yet... why/how would it be possible, that the Earth... is not round, but is flat?! You have to think that is pretty weird don't you?!
Also, understand... WHY the Sun, the Moon, and all planets are round. The reason has to do with gravity. You know gravity exists because when you drop things... they fall down! They never fall up, or in any other direction... except down, and the reason is because of gravity. Now... the reason giant massive objects in space (like stars, moons and planets) are all round, is because they are so large, that they collapse under their own gravity in space, and as a result... become round. Think about space... in space there is no up, no down, no right, no left, no East, no West, no North, no South, and no direction of any kind... so, pressure all around an object in space is equal across every part of that object. If there is no place in which pressure or force is greater or lesser than any other... the object when/if it is so heavy that it collapses under its own gravity it must become round, because it became crush uniformly. Think of tin foil... you can fold tin foil, and flatten it, because you are creating force in ONE direction, but... if you create crushing force on the tin foil equally... in all directions... it becomes a round ball! This is why planetary bodies are like round balls... including the Earth.
Also, lets say, you were standing at a lighthouse, up on a tall hill/cliff, and you were watching it going away from you... eventually, it would disappear in the horizon, because the Earth is round... if the Earth was flat... it would just keep getting progressively smaller, but it would still be visible.... basically forever if you had a telescope. For example, if the Earth was flat, you could stand off the beach on the East Coast of the United States, look through a telescope, and see Europe... but you can't! Its not because Europe is too far away, after all... telescopes can see planets that are MUCH further away than Europe. The reason you cannot see Europe from the East coast of the United States with a Telescope... is because the Earth is round, and because your vision cannot bend... along with the shape of the planet, at some point... your vision ends with the horizon. Buy a telescope, go to a beach, or very large body of water, and try it for yourself, you will see that your vision disappears as the curve of the Earth rounds off.
Think about these things, and ask yourself... what makes more sense based on this information. I have explained how and why it makes sense that the Earth is Round, what logic or evidence is there to explain that the world is flat?! There really isn't any at all... except that it seems flat sometimes, and the reason it can seem like that sometimes... is because of how small humans are, compared to how insanely massive the Earth is. However, if you were to stand on a very high mountain, you could readily see that the Earth is round, you could see it curve. I believe that is how you could know for sure.