What events from The Adventures of Tom Sawyer does Huck mention in the first paragraphs of the story?

Tom Sawyer and Huck's discovery of a trunk filled with gold coins in a cave after witnessing events in a cemetery and a haunted house in The Adventures of Tom Sawyer are alluded to in the opening chapters of The Adventures of Huckleberry Finn.
In the opening paragraphs, the narrator Huckleberry Finn mentions that he and Tom Sawyer "found the money that the robbers hid in the cave, and it made us rich. We got six thousand dollars apiece—all gold." It is this treasure that Huck is worried about in chapter 4 of The Adventures of Huckleberry Finn. Huck becomes alarmed when he sees the footprints of his father's boot-heel "made with big nails, to keep off the devil." Frightened, Huck rushes to Judge Thatcher's. There, he begs the judge to take his one hundred and forty dollars and the six thousand of his share of the treasure, as well. The puzzled judge tells Huck he will "buy" it for a dollar, suspecting that Huck is threatened somehow. Indeed, Huck is worried that his scoundrel of a father will try to take this money from him.
The six thousand dollars is in gold coins that were hidden in the cave by Injun Joe. Huck and Tom Sawyer's discovery was made possible by the fact that they overheard three men in a cemetery one night. There they witnessed Injun Joe kill one of the men. Later, the boys dug for the treasure at an abandoned house, but they had to hide because men arrived. As these men talked, Huck and Tom recognized the voice of Injun Joe. Then, the boys saw the men try to bury their booty. However, as they dug, they discovered another treasure of gold coins. Having noticed the boys' new shovels, however, the men decided to move this treasure, believing that others were previously digging for it.
In a later chapter, Tom and Becky were lost in a cave and remained in there for some time despite a search for them by men in the town. Fortunately, Tom finally found a way out. A week later, Tom had Huck accompany him to this cave, where they found the treasure of gold that Injun Joe buried. The boys were awarded the gold, and it was invested for them. This is the money that Huck alludes to in the first paragraphs of The Adventures of Huckleberry Finn. This is also the treasure that Huck tries to give to Judge Thatcher.