iPhone 6s backlight pins

Hello. I wish to find out which two from the four pins from the LED backlight actually use 16v. Which is plus and which is minus? I have a backlight issue that it's to expensive to repair around here and need a cheaper solution. Unorthodox maybe, but this doesn't involve motherboard soldering.

Thanks. I figured it out. Since they are LEDs... They don't get burned when the polarity is wrong. So I found out that the first and the third contacts, starting from upper side, were those I wanted. Again, I didn't pay attention to polarity. It worked. If it didn't, then I just needed to solder the wires the other way. I have tested with a 16v transformer from a printer and from an iPhone 4 and 6. iPhone 4 would only power up half of the LEDs. But you MUST have it already connected, or else it will only send juice for a fraction of a second. Tested on my tongue and with a power meter. It's good that it's only a jolt, so it won't blow up it's filter or whatever it has before the LCD connector. Was fun. Now I have 2 apples on a branch lmao.