As shown in the Manga and the Anime, Enel survived along with the Ark. He then Embarks to Fairy Verth
The Moon.
In the Manga it shows his adventures on the Moon. But what happened? I didn't understand the situation that happened. What exactly happened on the Moon?
There's an article on One Piece Wiki which describes the mini-series. I've copied the summary below for completeness, but you might prefer to read it there since it has relevant links to other articles.
While exploring the moon, Enel finds a small robot in a crater and attacks it. The electricity, instead of harming it, recharges it (much to Enel's disappointment). The robot, identified as First Lieutenant Spacey, finds its fallen comrades - Macro, Galaxy and Cosmo - and weeps over them while Enel watches on, impassive. While the Lieutenant is mourning, a fox-like Space Pirate attacks it from behind with an electrocuting spear. The Space Pirate, then attempts to attack Enel, who nonchalantly phases through the spear, attacks, and defeats it in retaliation. Enel, then sees a huge explosion in the distance, and is angered by what appears to have destroyed his ark, Maxim. Meanwhile, over at the area of the explosion, three more Space Pirates are converging, planning to excavate the moon for its treasures. Enel soon appears at the excavation site.
In the meantime, the shocked, but still alive Lieutenant Spacey reminisces about why he and his comrades came to the moon in the first place. An old man named Professor Tsukimi made them on Machine Island, and one day, while watching the moon and eating snacks, a huge explosion happened on it, much like the one that destroyed Enel's ark. The professor, shocked, swallowed his dumpling without chewing, resulting in him suffocating to death.
After burying the professor, the four Spaceys traveled to the moon (each one with a balloon) to take revenge on the one who caused the explosion that resulted in the accidental death of the professor by suffocation. Upon reaching the moon, they find the same space pirates that destroyed Maxim, and despite overwhelming odds, they fought the captain of the Space Pirates. In the end, however, all four of them were defeated.
In present time, Enel attacks the Space Pirates and destroys the entire excavation site with his lightning powers. This uncovers a canal that he intends to explore. Before he can do so, however, Lieutenant Spacey (towing his comrades' bodies behind him on a sled) rushes up to him and thanks him for avenging him and his comrades' "father".
Enel shocks the Lieutenant, and all of his comrades out of sheer annoyance, and goes on to explore the dried-up canal, coming upon a cave. Inside the cave is a huge Mayan-esque city, which he decides to electrocute as well. The resulting surge of electricity awakens not only the city, but a horde of ancient-looking Spaceys as well.
The entire city, having been activated, all of the ancient Spaceys, as well as the four "new" ones that Enel had just met, rush to thank him, much to his confusion. Enel, then studies a wall painting, and realizes that the original Birkans, his ancestors, one of which is Professor Tsukimi, came from the moon. Looking around, Enel sees endless followers, and an enormous amount of "vearth", and decides that the "Fairy Vearth" was everything that he had wanted.
