In Mormon 4:23, Mormon wrote that he had been to the Hill Shim to remove the records. He decided to get the records, protect them, and do whatever he could to complete his responsibility. He needed to hide the records and convey them to his son Moroni. It was clear that he was not going to be able to protect them for very long.
And here Mormon already mentions the Jaredites (9:23), whose demise was a foreboding precursor of what would happen to the Nephites and also a prescient reminder to Moroni that he, someday, would be the one who would abridge the Jaredite plates of Ether.
Then in Moroni 9:24, Mormon wrote to Moroni, “But I trust that I may see thee soon, for I have sacred records that I would deliver up unto thee.” This has a strong connection with the way Mormon ended chapter 4: “And now, I, Mormon, seeing that the Lamanites were about to overthrow the land, therefore I did go to the Hill Shim and did take up all the records which Ammaron had hid up unto the Lord.” This was likely referring to the same situation, and since Mormon was saying, “I hope to see you soon,” he probably had just been to the hill. He was apparently saying to himself, I now have the records, and I have to get together with my son Moroni. I will write him this letter and tell him what is happened.