First, there is no point whatsoever in posting the same question in three consecutive posts! You are likely to be seen as a potential spammer and hence be blocked from accessing the forums.
However, in order to be able to have any chance of answering your question we need to know exactly which version of Music Studio you have and where, exactly, you bought it.
If you purchased it direct from Magix, you should have received a confirmation email, which should have included the needed serial number. If you purchased a boxed version the number should be on or in the box; if it is not, you need to go back to the seller and ask for it.
Also, please be aware that these are user-to-user forums, not a contact point for Magix support. As fellow-users we have absolutely no means to access your serial number.
Please read my earlier reply to the original poster. The situation is still exactly as it was before. Nobody here can send you anything, serial number or otherwise since all posters, with only very few exceptions, are fellow-users.
If you are prepared to give us all the requested details in a new thread we may be able to offer guidance to you.