Hi Rituparna,
It is good to hear that you are aiming for the certification, however you have to chose for which of the certification you want to go for ABAP also, Check the link below for getting more information on that,
Also with this you will need knowledge of syllabus that you have to cover and example of sample questions which would also be available on:-
https://training.sap.com/v2/certification/c_taw12_731-sap-certfied-development-associate---abap-w...
Study both the links thoroughly and you will get the help you are looking for.
Regards,
Saumitra