Hi there, do you mean you want to take the txt and change it so that it is shown as a date?
If so, you can go into the Power Query Editor and change the column from text or number to date, and it should convert it for you automatically.
I have tried right now. This is the error:
DataFormat.Error: No se pudo convertir a Date. Detalles: 20050701
Using Adventure Works DW Database, Table FactInternetSales, Column OrderDateKey. If I convert from integer to Date I get the error, but I can do it in two steps: Integer -> Text -> Date