The Hebrew text states,
כַּאֲשֶׁר צִוָּה יהוה אֶל מֹשֶׁה וַיַּנִּיחֵהוּ אַהֲרֹן לִפְנֵי הָעֵדֻת לְמִשְׁמָרֶת
which is translated as,
As Yavheh commanded Moses, so Aaron placed it before/in front of/in the presence of the testimony, to be kept.
The preposition לִפְנֵי means "before, in front of, in the presence of."
Gesenius, p. 680, wrote,
It does not mean "in." The Hebrew text does not even mention the "Ark of the Covenant," so there's no basis for the New Living Translation of "in the Ark of the Covenant," which would have required the phrase בָּאָרוֹן בְּרִית. However, this doesn't mean that the jar of manna was not "before/in front of/in the presence of" the tablets inside the Ark of the Covenant. My point was that the Hebrew text does not state "in the Ark of the Covenant."
Gesenius, Heinrich Friedrich Wilhelm. Hebrew and Chaldee Lexicon to the Old Testament Scriptures. Trans. Tregelles, Samuel Prideaux. London: Bagster, 1857.