Duplication in rows condional formatting

Hi Forum,

Looked though previous posts, but cannot solve my problem.

I have spreadsheet that i need to highlight duplicate rows with CF ideally. All Cells need to match across all columns(A-AB) to qualify as duplicate.For me its a made tricky cuz the sheet has 31000 rows.

I have completed unique filter and saved result but need to show duplicates. The main aim is to keep the sheet in same order to present back to client .

Any suggestions would be a great help.

Thanks in advance