I suggest using PowerShell when it comes to copying large files between your local/AWS. Use Write-s3object cmdlet to copy your .bak file after making the backup through SQL. You need to download Powershell for AWS

-    Upload to S3
$s3Bucket = 'yourbucketnameinaws'
$backupPath = 'D:\BKUP_TEST_AWS\'
$region = 'us-east-1'
$accessKey = 'writeyourkeyhere'
$secretKey = 'writeyoursecretekeyhere'
$fileName = 'TEST_backup.bak'
$filePath = Join-Path $backupPath $fileName
Write-S3Object -BucketName $s3Bucket -File $filePath -Key $fileName -Region $region -AccessKey $accessKey -SecretKey $secretKey

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