Initializing SD card...Wiring is correct and a card is present.

Card type:         SDHC
Clusters:          956672
Blocks x Cluster:  8
Total Blocks:      7653376

Volume type is:    FAT32
Volume size (Kb):  3826688
Volume size (Mb):  3737
Volume size (Gb):  3.65

Files found on the card (name, date and size in bytes):
SYSTEM~1/     2019-08-30 08:39:38
  WPSETT~1.DAT  2019-08-30 08:39:38 12
  INDEXE~1      2019-08-30 08:39:42 76
DCIM/         2020-05-27 12:00:02
  100MEDIA/     2020-05-27 12:00:02
    SUNP0002.JPG  2020-05-27 12:44:02 537174
    SUNP0006.JPG  2020-05-27 12:55:08 615015
    SUNP0010.JPG  2020-05-27 13:08:24 525686
    SUNP0014.JPG  2020-05-27 13:20:54 436538
    SUNP0018.JPG  2020-05-27 13:23:44 691307
    SUNP0022.JPG  2020-05-28 12:00:28 746742
    SUNP0024.JPG  2020-05-28 12:04:26 611900
    SUNP0025.JPG  2020-05-28 12:05:16 608412

void myCAMSaveToSDFile(){

....

  //Construct a file name

  k = k + 1;

  itoa(k, str, 10);

  strcat(str, ".jpg");

    ↓

  while(1) {

    k = k + 1;

    itoa(k, str, 10);

    strcat(str, ".jpg");

    if(!SD.exists(str)) break;

  }

void setup() {
....
#if defined (OV2640_MINI_2MP)
  myCAM.OV2640_set_JPEG_size(OV2640_320x240);
    ↓
  myCAM.OV2640_set_JPEG_size(OV2640_640x480);
....
  myCAM.OV2640_set_Special_effects(BW);

  pinMode(BTN_PIN, INPUT);
  pinMode(LED_PIN, OUTPUT);
}

void loop(){
  myCAMSaveToSDFile();
  delay(5000);
    ↓
  if ( digitalRead(BTN_PIN)==HIGH ) {
    if ( !writeStatus ) {
      writeStatus = true;
      digitalWrite(LED_PIN, HIGH);

      myCAMSaveToSDFile();
      delay(5000);

      writeStatus = false;
      digitalWrite(LED_PIN, LOW);
    }
  }
}