# sample date
date_as_string <- "2019-04-30 11:29:24"
# without lubridate
format(x = as.POSIXct(x = date_as_string),
format = "%d-%B-%Y %H:%M:%S")
#> [1] "30-April-2019 11:29:24"
# using lubridate
format(x = lubridate::ymd_hms(date_as_string),
format = "%d-%B-%Y %H:%M:%S")
#> [1] "30-April-2019 11:29:24"
Hope this helps.