Comparing this statement with Hebrews 9:4, it would seem that Solomon, now that the sacred chest had reached its final resting-place, and stood in a large chamber surrounded by tables 2 Chronicles 4:8, removed the pot of manna and the rod from the interior, and set them elsewhere in the holy of holies.
Related Commentaries of 1 Kings 8:9
1 Kings 8:9
9 There was nothing in the ark save the two tables of stone, which Moses put there at Horeb, when the LORD made a covenant with the children of Israel, when they came outc of the land of Egypt.