Translating short words like in, at, or to can be tricky because there’s no general rule for this in Italian. But here's something to make your life easier: usually you can use the word in before the name of a room.
When talking about a specific room, you can also use in combined with il, la, etc.
Lui cucina nella cucina.
He cooks in the kitchen.
The word table is very special in Italian. When you’re talking about a table as just a piece of furniture, you use the masculine noun tavolo.
Il tavolo è verde.
The table is green.
Le chiavi sono sul tavolo.
The keys are on the table.
But things change if you are talking about a table that is set up for eating or if someone is eating at a table! In these cases, you’d use the feminine word tavola.
Another special word in Italian is scala. The singular noun scala usually means ladder. But the plural form scale normally refers to stairs instead.
Hai una scala?
Do you have a ladder?
Lascio i miei stivali sulle scale.
I leave my boots on the stairs.