I have a world on PC with some good items in that I'd like to put on my 3DS, is this possible at all?
Nope. Different formats. They're essentially two totally different games and the save file format is completely different.

technically although itd be easier and take less time to make you world again as youd have to have to coding languages connect to eachother which im unsure about then theres the whole how would the player item interact with the version cause the most recent ver . 1.4.4 us different then the most recent 3ds version 1.2 so new items nope new npc nope any mods you better code them yourself and even then they wont interact with the official one so its theoretically possible however most certainly not worth itBut could we make a converter?