Well, if you had yyyymmdd i would say go into power query, split the column into 3, yyyy, Mm, dd and then merge again in the format dd-mm-yyyy. Then convert to a date. But I have no idea how to turn your week number into a date. I guess you will need to do it in Excel manually.
* Matt is a Microsoft MVP (Power BI) and author of the Power BI Book Supercharge Power BI.