AWS: Split buffer in multiple pieces in lambda function

I have a problem.

In my lambda function I have to split a file from an s3 bucket into multiple parts to perform a multipartUpload to copy the file to the same bucket but to a different folder.

I tried different methods but nothing works, so I started to turn the file into a Buffer, now, how can I split the Buffer into limited parts based on the memory size?

Example: my file is 1000MB in size, how can I divide this buffer into 10 parts of 100MB each?

Here my code:

  const fileBuffer = Buffer.from(srcKey);
  console.log('##### 2. BUFFER: ', fileBuffer);

  // I tried this but seems doesn't work in the way i want...
  const numOfParts = Number((fileSize / (100 * 1024 * 1024)).toString().split('.')[0]);
  const chunks = fileBuffer.slice(numOfParts);
  
  console.log('###### 3. NofParts: ', numOfParts, ', Nchunks: ', chunks.length);