Retrieve data in .each() and create columns

Hi,

I'm kind of a begginer in PowerBI and I'm facing an issue :

I've got an existing table with datas in it, being updated every month by someone else.

In this table I've got colums named MonthCode, OperationalBase, Action like so :

5, Dijon, 6

5, Nevers, 2

5, Beaune, 9

6, Dijon, 5

6, Nevers, 8

In this example, I've got no data for Beaune in the month of June and I'd like it "write itself".

By that, I means that whenever a new month is detected (7 for this example), every city will be here no matter what, even if no data was inserted.

I'm trying to create something in the Power Query editor but I've got no bases.

Here's what I got right now :

 Test = List.Generate(
    ()=>0,
    each _<12, each _+1,
// check if _ exists in DataTable
    each Table.Column(
            [monthCode = _+1, city = "Dijon", action = DataTable['action']['Dijon']]
            [monthCode = _+1, city = "Nevers", action = DataTable['action']['Nevers']]
            [monthCode = _+1, city = "Beaune", action = DataTable['action']['Beaune']]
// maybe automatically create the rows without adding them manually to the code ??
        )
    ),

I'm not even sure if what i'm asking is possible, but I'd be grateful if you could help me.