How to solve data format issue in Auto Arima , Prophet forecasts with R?

Question

This is dataframe (df)

         ds         y
1 2020-09-25 42,034.88
2 2020-09-24 41,806.37
3 2020-09-23 41,876.26
4 2020-09-22 41,828.91
5 2020-09-21 42,174.13