The hook is the only part of your setup that actually holds the fish, and the one most often got wrong. Sizes run from 10 at the smallest up to 4/0 at the largest, counting down to 1 and then up through the /0 sizes, so a 1/0 is one step larger than a 1 rather than ten times smaller.
Two things constrain the choice. Every rod states a hook range it accepts, and every bait or lure states the size it is tied to. The hook has to satisfy both, which is why a heavy rod paired with a small bait often will not fish at all.
Bigger is not better. An oversized hook is visible to a wary fish and sits badly in a small mouth, so a fish will take at it and miss. Match the hook to the bait first and the rod second, and only go up a size when you are losing fish to pulled hooks rather than to refusals.
The shop stocks 10 down to 4/0. The six larger sizes exist in the files but carry no price in any currency, and every lure that asks for one is likewise unbuyable, so they are marked here rather than hidden.