I need help with my new SMD LEDs for my car.
Source voltage 12V , car usually use 2X 12V 5W hallogen lights
I now have 2x 24pcs SMD 3528 white LEDs.
What resistors do I need ?
I specify that normal lights are in parallel also.

 

Welcome to AAC!

I now have 2x 24pcs SMD 3528 white LEDs.

You have given the physical dimensions of the LEDs. We need a part number to determine allowable current.

The first datasheet I found gave a 50mA current for several colors, but white had a lower peak (pulsed) current.

Forward voltage for white varied from 2.8-3.6V, which could affect brightness if you try to have the maximum number in series.

Are these interior lights? Some locales have restrictions on exterior lights.