Trouble with geting the required data from a pivot table

So I am doing a project for school and it involves the use of a pivot table

I can get the Pivot table created but I cannot figure out how to manipulate the data to solve for the question.

the question is

Sales Tax Data
(note – the data for this problem has been fictionalized)
The enclosed spreadsheet consists of two months worth of data received by the city related to monthly sales tax remittance. With this data, provide the following:
• Create a new sheet that has totals by account number for each month that compares the year-over-year changes, including the percentage change. Group all accounts listed under “Specific outlet information is not available” as one item for this comparison. Please keep in mind that the same account number may be listed more than once during a month, and sometimes businesses come and go over the course of a year.

any help would be greatly appreciated