Please note, Rolex watches made after 2010 no longer have sequential serial numbers and cannot be dated this way.
To find your serial number you must remove the strap at the 6 o'clock position and you will see it engraved on the case between the lugs.
It will be between 5 and 7 digits and may start with a letter. The Rolex model reference can be found between the lugs on the opposite side of the watch, it is between 4 and 6 digits and is numbers only. This model reference will decode to tell you the model of watch, the material it is made from and the style of bezel it should have. If available a link to the user manual for that model will be provided as well. Please note this part is in beta and the bezel/metal info may not be accurate, I welcome any feedback on this.
This does not validate if a watch is genuine or not, it purely translates the date code to find the year of manufacture and decodes the model reference. If the watch type was not being manufactured during the year suggested by the serial number or if the model reference suggests something different to what you have then it tells you that further investigation may be required.