How does pet microchip ID work to reunite pets with owners?

I registered my cat’s microchip ID with 2 organizations: “found.org” and “pet key.org”.

I’m not sure how the system works in the event that my cat becomes missing.

Will the finder of my lost cat be able to access my contact information with my cat’s microchip ID number even if the finder doesn’t know of the organizations that I registered my cat with?

I did a google searched of my cat’s ID code number and came up with nothing.

How many organizations do you register your pet’s microchip ID with?