It's a simple warning (of a mod, hence not a game error) that some prop of 1 or more assets is missing. The asset (probably building) itself WILL be perfectly fine without it.

So no, you DON'T need help finding that prop (no one will do so anyway). What you need is understanding of how MODS (like LSM you mentioned, anything that changes the original game) and ASSETS (just stuff to place, from entire buildings to a simple tree) from the workshop work, where potential interaction (if any) is and then your 'situation' will sort itself out.