Hook: Floor Small (Green Square)The Industrial Fire Pit decoration fits into a small green square floor hook.
Hook: Floor Medium Narrow (Blue Rectangle)The Industrial Fire Pit decoration fits into a narrow blue medium rectangle floor hook.
How to Get an Industrial Fire Pit Decoration
Cartel Pack Decorations
The Industrial Fire Pit decoration can be dropped from Seneschal's Stronghold Packs, which were released on the Cartel Market and bought with Cartel Coins. Cartel Packs, including the Seneschal's Stronghold Pack, include a random selection of items from the Seneschal's Stronghold collection of items. You aren't guaranteed to get an Industrial Fire Pit decoration from a Seneschal's Stronghold Pack, but it is one of the few ways to get an Industrial Fire Pit deco apart from buying it on the GTN from another player.
If you're looking to get a Industrial Fire Pit, the easiest way to get it is to head to the Galactic Trade Network (GTN) in SWTOR and buy it with credits from another player. If it's very rare and not available on the Cartel Market, you could try buying from the GTN and hope you get it.