Explanation

You must apply to the judge for a pardon 

آپ کو جج کے پاس معافی کے لیے درخواست دینی چاہیے۔

We use “apply to” when we say where we are applying. 

We use the" to" preposition with "apply" because apply to is used where we say for applying

for example: in the above sentence " we someone to  apply for pardon application to the judge"