Help with converting date using EOMonth formula

Hi there, I am working with a dataset of thousands of rows. Each row has a date field. The data I have extracted have 2 types of date fields. One that has "dd/mm/yy hh:mm" and another that has "dd/mm/yyyy hh:mm". I am running a 'EOMonth' formula on the column next to them so that I can bring all values that fall in a month to a particular day. However, when I run the EOMonth next to the format that has "dd/mm/yyyy hh:mm", it is generating a value error. I have attached a copy of a sample spreadsheet.

I am looking for a formula or a method with multiple formulas to easily convert thousands of rows of "dd/mm/yyyy hh:mm" to an end of month date.

Thank you in advance!