There was nothing in the ark except the two tables which Moses put there at Horeb: Exo 40.20 and Deut 10.5 record that Moses placed these tablets in the ark. According to Exo 16.32-34 and Num 17.10-11, the ark also contained a jar of manna and Aaron’s walking stick (see also Heb 9.4). The English word tables refers almost always to the place where people sit to eat. Therefore more recent versions use the word “tablets” (New Revised Standard Version, Revised English Bible, New Jerusalem Bible, New American Bible). Some translations make explicit that these were “stone tablets” (Good News Translation, Bible en français courant, El libro del Pueblo de Dios) or “flat stones” (Contemporary English Version). Anchor Bible says “tables [of the law],” making explicit that these tablets contained the law that God had given Moses.
The adverb there, which Revised Standard Version has added as the sense of the Hebrew requires in English, refers to the inside of the Covenant Box. In some languages it may be better to translate the meaning more clearly by rendering which Moses put there at Horeb as “which Moses put in the box when it was at Horeb.”
Horeb is another name for Mount Sinai (see Sirach 48.7). The name Horeb is often used in Deuteronomy. Since Horeb refers to a mountain, Parola Del Signore: La Bibbia in Lingua Corrente says “Mount Horeb.” In keeping with its usual practice, Good News Translation translates Horeb as “Mount Sinai” since Sinai is the better known name for most readers today (also Contemporary English Version, Beaumont). If the name Horeb is retained in the translation, a footnote should be added to explain that it is the same as Sinai.
Where the LORD made a covenant with the people of Israel: Made a covenant is literally “cut [a covenant]” (see the comments on 1 Chr 11.3). In many languages a literal translation of the verb “cut” will not express the meaning of the Hebrew. Also, in a number of languages it will be necessary to add the word covenant as Revised Standard Version has done. A covenant is an agreement that two persons or groups of persons make in which both promise either to do or not to do certain things. In the ancient Near Eastern world of the Old Testament, animals were sacrificed and cut up as part of the covenant-making ceremony. From this comes the technical phrase “cut a covenant.”
People of Israel is literally “children of Israel” (King James Version). Often in the Old Testament this Hebrew expression refers not to young people, but to the Israelite people as a whole (compare 1 Chr 6.64). So the Revised Standard Version rendering is preferable to a literal translation. Another possible model is “the Israelites” (Bible en français courant, Nouvelle Bible Segond) or simply “Israel” (Luther).
In some languages this entire verse may have to be restructured and broken down into several sentences to make it sound more natural. Parole de Vie gives a possible model, which is:
• In the box, there were only the two [stone] tablets of the law. After the Israelites left Egypt, the LORD made a covenant with them on Mount Horeb. It was at that time that Moses placed the tablets of the law in the sacred box.
Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on 1-2 Chronicles, Volume 1. (UBS Helps for Translators). Miami: UBS, 2014. For this and other handbooks for translators see here .

When was the msnnna & Aaron’s rod removed
I don’t believe that there is any data about that but it’s probably safe to assume that it was removed during the Philistine capture or, more likely, during the Babylonian raid and capture.