You will need to modify the source code. The problem is that you are changing the grammar, as well as the vocabulary. If second where grammatically the same as 2, and could safely replace it everywhere, you would just over-record the 2 file.
The definitive level of detail for this sort of question is provided by the source code. My guess is that it is a simple to medium difficulty change, but, if you are not comfortable with the change, you should go to the jobs forums and recruit someone with coding experience.
If you need to ask questions, you would need to use a developer mailing list or IRC channel, but don’t expect complete solutions.
Incidentally, the Asterisk code does not specify the recording format. It chooses the best file extension from those available, given the target codec.
The literal answer to your question is that you simply replace the contents of the file, in your language version, however the result will be that Asterisk says “you are number second in the queue” and, when reading out the phone number 555 1212 in English style, will read it as five five five one second one second.
it is easy way to change “digits/2” to costum language with "second ", but when i want to use
saynumber(2) application it will play “second” instead “2”