"store room" is correct and usable in written English.
You can use it to refer to a room in which items are stored. For example, "I need to get something from the store room before I start work today."
When downstairs was a store room, she added, "I could stay the night there.
The video below shows a group of Parisians hiding in a kitchen store room.
"One day he'd finished having sex with me in a store room.
Inside is a space that more closely resembles a store room than a restaurant.
"Baby, listen to me... .. Without warning, the store room wall blows up.
They made their way to the second-floor store room, broke down the door and dressed themselves in officers' uniforms.
The window was being housed in a store room close to where the fire broke out, York Minster Police said.
The building had originally been a dwelling, later converted variously into stables, a bakery and a store room.
One doorway appeared to lead to a store room and the other a continuation of Tutankhamun's burial chamber.
