So pretty much go on the front title page of terraria and go to settings and then to video and then to map enabled turn it from off to on Hope this helped bro!

As Kazzymodus said, you may be able to enable the map in settings, general (note that these settings may only be visible from the main menu, not when you have a game load). But a disabled map can also be caused by an insufficient graphics card. Terraria hides the map if it doesn't think your computer can handle it.

There actually is another way to reveal the whole map. The way you're talking about is a mod called Hero's Mod. It's like a creative mode mod for messing around and such. Another mod called Fargo's Mutant Mod has an item that reveals the whole map, but its actually earned instead of cheated.

MoreTerra is a simple map viewer that allows you to export a full PNG of the map you’re on. It’s a simple-to-use program that allows you to crop the image, draw on it, and even pinpoint specific chests with the click of a button. It also gives you the ability to see Shadow Orbs, Gold, and Diamonds.