Where did Aaron die? At the Lord’s command Aaron the priest went up Mount Hor, where he died on the first day of the fifth month of the fortieth year after the Israelites came out of Egypt. (Numbers 33:38, NIV)
The Israelites traveled from the wells of Bene Jaakan to Moserah. There Aaron died and was buried, and Eleazar his son succeeded him as priest. (Deuteronomy 10:6, NIV)

These passages seem to say that Aaron died in different places. How can they be reconciled?
Numbers 20:25&ndash;29 says (NABRE)


  Take Aaron and Eleazar his son and bring them up on Mount Hor. Then strip Aaron of his garments and put them on Eleazar, his son; but there Aaron shall be gathered up in death. Moses did as the LORD commanded. When they had climbed Mount Hor in view of the whole community, Moses stripped Aaron of his garments and put them on Eleazar his son. Then Aaron died there on top of the mountain. When Moses and Eleazar came down from the mountain, all the community understood that Aaron had breathed his last; and for thirty days the whole house of Israel mourned Aaron. 


The New American Bible has a note to this passage; it states 


  Mount Hor: not definitively identified, but probably to be sought in the vicinity of Kadesh. According to Dt 10:6, Aaron died at Moserah (cf. "Moseroth" in Nm 33:30–31), which is apparently the name of the region in which Mount Hor is situated.


That's one possibility.

Similarly, the Pulpit Commentary on Deuteronomy 10 states


  As Aaron died there, Mosera must have been in the vicinity of Mount Her [sc. Hor].