What is the American measurement equivalent of 3см.л in Russian
I think this is a typo. The original is probably 3 ст. л, which means 3 tablespoons (an abbreviation for столовые ложки). 

Note that, in Russian cursive handwriting, a т looks like a Latin small m, and can also, with the wrong amount of slant and writing speed, look like a Cyrillic small m. I don't know where cursive handwriting can have come into play in the design of a modern packaging, but it is one small pointer. 

This interpretation also makes sense from a culinary point of view. I don't know the concentration of your seasoning, but 3 tablespoons sounds roughly feasible for 900 g of rice, which is quite a lot of rice, especially if measured dry. 3 cubic centimeters would not only be a weird unit to use in kitchen measurements (ml is the common one) but also it would only be a sufficient amount if you are using something like pure MSG crystals. 

Russia does not use the Imperial system, so having a Russian recipe expressed in tablespoons is even less precise than an American recipe doing so. A Russian seeing this recipe would just use any real eating spoon in their cupboard to do the measuring. So, be prepared to treat this as a starting suggestion only, it might need some (or a lot of) tweaking to work well in your context.