Try in B1:
=IF(AND(COUNTIF(A:A,A1)>1,COUNTIF(A1:$A$1,A1)=COUNTIF(A:A,A1)),A1&" "&COUNTIF(A:A,A1),"")
and copy down
and for conditional formatting, select the used range of column B and try this formula:
=B1<>""
to highlight the names in the list (column A), try this formula in conditional format:
=COUNTIF(A:A,A1)>1
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