converting arbitrary date time format to panda timeseries

Question

I'm trying to convert a column in a dataframe to timeseries, the values in the column are strings and they are in the following form: 12/10/202110:42:05.397 which means 12-10-2021 at 10:42:05 and 397 milliseconds. This is the format that Labview is saving the data into a file. I'm trying to use the following command, but I can't figure out how to define the format for my case: pd.to_datetime(df.DateTime, format=???) Note that there is no space between year 2021 and hour 10