Hi @SwJ23 , thank you for your answer! 😊
I did not know what the question mark was for in this type of query, so thank you for the information 😁
I tried using your solutions, but I got other types of errors.
When using this query:
'formatDateTime(item()?['DueDate'],'MM-yyyy')' eq CeMois
I get the following error :

Error details: One or more fields provided is of type 'Null', a different type is expected.
I have checked and my 'DueDate' column is of Date format in excel, I do not understand this error.
When trying to use this query :
'formatDateTime(['DueDate'],'MM-yyyy')' eq CeMois
I get and error saying the expression is invalid, I had tried this expression and gotten the same error before so I figured that I had to put Item in front of the column name for the query to work.
Lastly I need the full 'DueDate' in my table because I am sending a reminder with the full date in it, and the day of the task is important, so I don't think I can match it to the format of the variable.