I plan on uploading something soon that is going to include some TS3 store content. My question is, can I put store content in the upload? (It is going to be a clothing item)

This item is a pair of women's boots that cost 0 Simpoints.

You can use content from the store, either pay or free, in your upload. You cannot INCLUDE it with your upload though. You may want to read the Creator Guidelines regarding uploading, as this question is already addressed as well as lots of other things.

i'm not sure if this is applicable to this particular thread, but... i kinda wanted the site to distinguish the requirement of the store items on the required packs part of the description with some sort of symbol to say quickly and simply that it references a store item that the user must have "purchased" from the store without having to select the item to read that it is strictly to modify a store item and is not the item itself.