Filtering Grouped columns

I have a table with more than 12000 records.

The PK column should not have duplicate values, but unfortunately it does.

I want to identify these records and I am looking for an easy way to do this.

I thought I could find these records grouped by the PK column and then applying a filter to that column.

Is there any expression that we can use in the filter box to get only groups with more than one record?
Something like count(PK) > 1

Or do I have to write a script to do this? :(