Info about Microsoft Sql Server 2014 Licensing and Pricing.

Hello,

I have a HPE ProLiant Server (Operating System:Sql Server 2016,16 core). I want to buy a license for Microsoft Sql Server 2014 (we are 40 employees,who must work on the database,at the same time) and all of us need 1 user to connect to db (sa).
What must I buy for company?Which license? The most beneficial for the company.

Thank you a lot!