I want to ask if this is considered as Bida’h (Innovation):
Let’s say someone commits a sin, he then asks for forgiveness, but this person also asks Allah (SWT) to show him, the number 313 if He has forgiven Him.

(For example, you could see the number on the street, or on a licence’s plate, or someone could mention it during a conversation etc…)

(This person also doesn’t believe that he has been forgiven until he sees the number, and depends on it to know whether he was forgiven or not)

Does this count as Bida’h?

This is not the right way of asking forgiveness. Allah is all Forgiving and Merciful. One cannot put conditions. What is important is for one to be sincere in asking Allah’s forgiveness