If you want to get a job in Serbia, it is necessary to submit a diploma with the documentation you attach to regulate your residence status (visa D or temporary residence). It does not have to be nostrified.
The document you are submitting for the purpose of regulating your residence status is a diploma, certificate, or other public document on the appropriate type and level of the required professional qualification or education. It is necessary to attach a certified translation of this document.
However, there are cases when it is necessary to nostrify the diploma - most often when a foreign citizen wants to continue their education, i.e. studies in the Republic of Serbia. However, it may happen that nostrification is necessary because the employer requires it. If you need to nostrify your diploma, you can do it electronically, and you can find detailed instructions for initiating the process of recognition of foreign primary, secondary and higher education documents in the article on recognition of diplomas.