How can I fix my iPhone it’s not reading my SIM card because I drop it in water

Unfortunately, the damage is likely going to be far more than a SIM card problem.

Make an appointment at the Apple Store or take the phone to an authorized Apple service shop to let them run some tests on the phone and go over your options with you.

You can find a list of authorized service shops in your area by using this link: Find Locations

You make an appointment at the Genius Bar of your local Apple Store or take it to your local Apple authorized service provider and pay for a replacement phone.

Liquid damage is not repairable.

iPhones are water resistant, not waterproof.

Water damage is not repairable. You most likely will need to purchase a new phone.

Make an appointment at the Genius Bar to have it diagnosed.

Genius Bar Reservation and Apple Support Options - Apple