grammar - Use of number+ counter as a noun

I didn't know that you can use a number+counter combination as a noun, but it seems from this sentence that you can.

一番上に置いてあった一枚を手に取った
She picked up the sheet that had been placed at the top

Is this always true and can it be extended to numbers other than one, e.g.

一番上に置いてあった二枚を手に取った
She picked up the top two sheets

What is the alternative? i.e. what would I do if there was no counter word (other than a generic counter) and I hadn't previously introduced the thing I was talking about e.g.

Please pass me the top two plates from that shelf.

I can't use a generic counter because there are also other things on the shelf and the person wouldn't know which thing I wanted.

Answer

Yes, "Number + Counter" forms a noun, and therefore, it should be treated as such in a sentence. Since it is a noun, one can say 「～～は」、「～～が」、「～～の」、「～～を」, etc. It is just not the kind of "normal" noun that one will find listed in the dictionary.

There is also no limit to either the quantity or the kind of object for the expression to function as a noun as long as what the object is is clearly understood from the context.

A man who has been married 5 times might say:

「[最初]{さいしょ}の3[人]{にん}はメキシコ[人]{じん}だった。」

A woman who has eaten a dozen chocolates might say:

「8[個]{こ}はミルクチョコで、4個はダークチョコだった。」

Finally, how to say the following naturally and correctly in the situation that you described:

"Please pass me the top two plates from that shelf."

I would suggest:

「[棚]{たな}にあるお[皿]{さら}の[中]{なか}から、[上]{うえ}の[二枚]{にまい}を[取]{と}ってください。」 or

「棚にあるお皿のうち、上の二枚を取ってください。」

You would need to introduce at the beginning what objects (among all the things on the shelf) you are referring to before using "Number + Counter" = 「二枚」.