Convert date format "dd_mm_yyyy" in dataframe to "dd/mm/yyyy"

General Usage
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6

Maybe you could provide a MWE we could run and understand better?

The code below converts from Date type to String type in the desired output format.

using DataFrames, Dates
df = DataFrame(ddn = Date.(["1900_12_31", "1950_01_13", "1990_11_30"], "yyyy_mm_dd"))
df.ddn = Dates.format.(df.ddn, "dd/mm/yyyy")
df
 Row │ ddn        
     │ String
─────┼────────────
   1 │ 31/12/1900
   2 │ 13/01/1950
   3 │ 30/11/1990