I think this is the armored cable used.
I hope not... That’s AC armored cable. Commonly called BX cable.
Hopefully yours in MC, (Metal Clad) Cable
https://www.southwire.com/wire-cable/metal-clad-cable/armorlite-type-mc-isolated-ground/p/MC40
https://www.southwire.com/wire-cable/metal-clad-cable/armorlite-type-mc-isolated-ground/p/69599901
.