The purpose of the certification for MongoDB whether the associate developer or the associate DBA exams is to help with skills development by providing a proven certification of competency in MongoDB. This certification could definitely be used to help move a career into the IT sector by showing this skill in MongoDB.
In terms of our recommendations for certification, firstly I suggest you choose one of the learning paths (see this blog post). The courses in each learning path are designed to help you learn the necessary skills and knowledge to pass our certification exam.
The MongoDB courses in MongoDB University are free, however, there is a cost to certification. You can find out more details on certification on this page.
Hope this helps and good luck with your career choices,