If you look at the numbers upside down, they read 86, __, 88, 89, 90, 91. The number that fits this pattern is, of course, 87.
Therefore, the space as the picture is currently viewed should be filled in with L8.
It's hard to be sure with all this sand in my eyes, but I believe the desert is saying:
Firstly, the title and the fact that the only numbers used in the grains of sand are 1 - 12, hint towards a clock face.
From here, we can treat numbers as directions, such that from any given point, you just take the number given and travel according to the ...
Not sure if this is really on topic, since it's more about image manipulation than the puzzle itself, but I'll answer anyway (and keep it on topic by solving the puzzle at the same time).
You can convert them with photo manipulation software as follows:
1) Isolate a barcode:
2) Warp to stretch the stripes:
3) Convert to black & white (and ...