How to move files from my laptop to dropbox to free up storage on laptop?

I figured out what I was doing wrong and posted the working code for the community's benefit.

void uploadFile() {
  Serial.println("Running Upload_file: ");
  HTTPClient http;

  File file = SD.open("/240x320.jpg");
    if(!file) {
      Serial.println("Failed to open file for reading");
      return;
    }

    int len = file.size();
    char size[8];
    sprintf(size, "%d", len);
    
    static uint8_t buff2[27142] = {255};
    static unsigned char encoded[27142] = {255};

    int x = file.read(buff2,len);
    unsigned int base64_length = encode_base64(buff2, len + 1, encoded);
    close(file);


    Serial.print("Size ");
    Serial.println(size);
  
    if (http.begin(dropbox_uploadfile)) {  // HTTP
      String token_key = String("Bearer ") + dropbox_token;
      http.addHeader("Authorization", token_key);
      String args = "{\"autorename\":false,\"mode\":\"add\",\"mute\":false,\"path\":\"/Homework/math/Uploaded8.txt\",\"strict_conflict\":false}";
      http.addHeader("Dropbox-API-Arg",args);
      String arg2 = "application/octet-stream";
      http.addHeader("Content-Type",arg2);
      String wild = "The luck of the Irish";
      int httpCode = http.POST((char*)encoded); 
  
      String payload = http.getString();
      Serial.print("payload: ");
      Serial.println(payload);
  
      http.end();
  }
}

I posted an article on Medium with the download and list files commands, too, which you can find at this link. Yes, it's behind a paywall, but the first three articles are free.

https://medium.com/me/stats/post/1f755145f504