Account_id

My problem is that I don´t know the account_id for a bank account. I suppose that is something like "3632010000002301" but I don´r know how to find it.
I need it because I have a custom function that create a customer payment, that works well, and I need to add "account_id": "xxxxxxx" to the map in order to register the deposit of the funds in the right account, not cash.
Regards
Angel