The posters above are likely correct.
It does not look like a “cartridge” type faucet.
You probably just need to turn off the water pressure supplying that sillcock, usually at the water meter in most houses.
Then just open the valve a half-turn or so, to lift the washer off the valve seat to reduce friction, and then crank out the guts of the sillcock by turning the cap nut counter-clockwise until it is totally free and then twist out the valve stem by the handle, also counter-clockwise.
Then you should see a black rubber or plastic washer at the end of the valve stem, held on by a tiny screw.
You can buy new washers to replace your worn out one. They also often come with new screws.
There are lots of different sizes of washers and screws, so carefully remove the old screw, and bring it and the old washer and valve stem to a hardware or big box store to find exact replacements.
If the old screw is rusted in tight, soak it for a few hours in straight vinegar, then dry it off well, then apply some penetrating oil or wd40 to it.
Then gently bang the screw head a few times, straight down against a piece of scrap wood, to shock it enough for the oil to find little gaps in the rust to sneak through.
In an hour or so the screw should loosen up.
If you force it and it snaps off, you are SOL for sure, unless you can drill out the old screw and force in a new slightly fatter one.
Even if the valve seat is corroded and might ideally need grinding, you might be able to get away with just cleaning out the crud on it with some vinegar or CLR type calcium cleaner, and rubbing hard on its surface with a skinny wood dowel, or something like a plastic toothbrush handle.
Just to knock off the minerals and grit that will interfere with the new washer making a good seal.