I have blank smart card with operating system "COS".it is ISO-7816 standard. I want to create MF,DF and EF files. Is there API can I use to do that? Using C#? Or any open source SDK? My reader is ACR38F-101
Creation of files is covered by ISO 7816-9, but creation of the MF is clearly flagged as out of scope there. You definitely NEED a manual, since the 7816 family of standards is not enforcing ANY feature to be implemented and proprietary supplements are always possible, so the manual is required to supplement the standard. If COS (Card Operating System?) is all you know from the card, chances for success are slim.
All well-used libraries are either low level (APDU, so you still need the manual) or for a certain domain implying a fixed (and already existing) file structure from a official specification. Neither seems to be what you are searching.
The only good news is, that practically any reader will be supported by PCSC, so your specific brand and model have no influence. (It could be, however, that card and reader are no good match, so e.g. maximum transmission speed can't be achieved.)