Confirm that your microchip contact information is up to date! If you don't know whether your cat is registered, you can register their microchip number for free at 24PetWatch (https://www.24petwatch.com/)
Knock on doors for all your neighbors, including those who are adjacent to your backyard. Let them know to keep an eye out and not to approach, especially if your cat is shy. Sometimes it helps if they can take a photo or video to send you, so you can confirm that it is your cat!
Post on your local lists, including Nextdoor, Craigslist, or other neighborhood groups. Be sure to also check them to see if others have posted your cat!
Notify your local shelter and be sure to visit them to see if your cat is there. You'll want to visit regularly, since it can sometimes take a cat a while to find its way there after it is lost.
Petco Love Lost:
Petco Love Lost uses facial recognition to help match up lost cats with cats that have come into shelters and rescues. If you haven't already registered when you adopted, can register your pet there. You can also search!
don't give up:
It can take a while for cats to emerge from hiding, seek help, get picked up by neighbors or the shelter. Sometimes weeks or months! Don't give up hope.