What is the exact wing chord length and thickness for Boeing 747?
In general, you can get good general dimensions from the Airplane Characteristics for Airport Planning documents (Boeing). These documents include the overall dimensions and everything relevant for the airport. This does not include the chord length though.
To get more accurate dimensions, you can download CAD drawings from Boeing. I did this for the 747-400 and the 747-8I and measured the chord length in three places along the wing:

As you can see, the chord length varies between 14.84m at the root and 3.70m at the tip (before the winglet). The wing for the 747-8 has been slightly re-designed:

While keeping its basic structure and sweep, the wing is thicker and deeper, holding more fuel, and wider with raked wingtips.

(Wikipedia)
The differences in chord length are rather small (possibly less than the accuracy of these drawings):