Change 8 digit date format to 6

I have a spreadsheet from the U.K. where the date is in the format of dd/mo/year (8 digits). I need to delete the day so the format is only mo/year (6 digits). This is necessary to comply with the requirements of another software program which imports the data.

The spreadsheet is ten of thousands of lines so manual change is not an option.

Change the cell format.

Select the column of dates, then on the excel 'Home' tab, select the format dropdown (top centre), 'More number formats', 'Custom'

In the box under 'Type:' enter mm/yyyy then click OK.

That did it. Thanks very much!