Average DAX Formula in Power Pivot with Monthnum

Hi everyone,

Could anyone help me with this scenario:

I have a column which is a month number from the begining we named months of each year a number for example may 2023  is 86 then june 2023 is 87 and so on ...

i want to have average of sales (for 9 month) and also (2 months )ago  from the getdate() and with the help of this monthnumber,

I would appreciate for any help