kotlin stringTime to long

fun convertISOTimeToDate(isoTime: String): String? {
    val sdf = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS")
    var convertedDate: Date? = null
    var formattedDate: String? = null
    try {
        convertedDate = sdf.parse(isoTime)
        formattedDate = SimpleDateFormat("MMMMM dd,yyyy").format(convertedDate)
    } catch (e: ParseException) {
        e.printStackTrace()
    }

    return formattedDate
}