"도착분" => (items / materials) that has arrived / what has arrived / the arrivals.
분 has a few more meanings in addition to what you mentioned.
In 도착분, it is a suffix to mean a set of items or a quantity of materials being thought of as a unit).
It is a compound word, and thus won't be listed in the dictionary as an independent word (only 도착 and -분 are listed).
It derives from the same Chinese character 分 (divide, division) which means a minute of time.
"minute" is "an hour divided". When something is divided or separated, the results can be called with this suffix.
For example, "1/3" is read as "3분의 1" (삼분의 일).
Likewise: there are 감소분(the amount of decrease), 부족분(the amount short), 초과분(the excess amount), etc.
분 also means "powder" (of a compact, 粉 - 분, 분칠하다), or "an angry or mortified state" (憤 - 분하다, 울분).
thank so much!!!!!!!