Is there a defined counting system in Pali?
Are there any equivalent numbers which can be written in Hindu-Arabic numerals for numbers used in Pali

I found one here by Googling for "pali numerals": Pali Numbers - Ancient Buddhist Texts


  This is a list of commonly found Pāḷi numbers which occur in the literature.


What is the time period mentioned in ‘‘Sataṃ sahassānaṃ nirabbudānaṃ, Chattiṃsatīṃ pañca ca abbudāni"

The reference I cited above says,


  1 + 63 zeros: nirabbutaṁ


Ven. Sugato's translation of that sutta says,


  For more than two quinquadecillion years,
  Sataṃ sahassānaṃ nirabbudānaṃ,
  
  and another five quattuordecillion years,
  Chattiṃsatī pañca ca abbudāni;


I don't know if those are the same numbers; I can't count that high in English!