Q: hi i lost my iphone and i have my serial no. now what i have to do? i report it to the police but i want to know if apple can help to find it

If earlier, you activated Find My iPhone before the theft, there might be a chance that you can still track your phone on a computer from iCloud.com/Find

Marina,

Go to iCloud.com, login with your apple id and look for Find my iPhone. You can then locate it if you have that facility switched on, You can also Lock it remotely and/or Wipe it remotely.

Also, let your carrier know to block the phone if someone tries to use it with a different SIM Card.

HTH, T.

Please read Report a lost or stolen Apple product - Apple Support  You should report it to your carrier and the police.  If you enabled it, you may be able to use find my iPhone to see its location.  Apple does not get involved at all with lost or stolen devices.