new order of bill number as of date

[kghisla]

Hi, i need to change the order of bill number of an array, but i have an hard time.
If i try with SORT and then decide the column i need, it will change all the formulas.
please see dummy file attached.
I need the bills to be re-numbered and organized from the oldest to the newest.
the table below in how i need it.

any help would be greatly appreciated.

thanks in advance for your time.

Carlo