How do I transfer large files from NTFS-formatted external hard drive without error code -50?

Are you trying to use Copy & Paste to transfer the items? If so, then try Dragging & Dropping the items instead.

Edit: I would suggest moving a limited number of folders at a time in case the process is interrupted or has an error.

Even better would be to use the third party app Carbon Copy Cloner (CCC) to perform the transfer and it has a free trial period. If there are any problems copying a file, CCC will allow you to skip it. All errors are logged so you can look at the CCC log to see which items were not transferred.

I don't know if it has been fixed in modern versions of macOS – but the Finder used to have problems with copying very large numbers of files at once, and would often return an error code -36 (a generic file error) if you tried it.

A workaround was to do a folder-to-folder "backup" in Carbon Copy Cloner.

"external hard drive without error code -50?: [...]I bought a new external hard drive (#2) so that I can transfer all the contects from Hard Disk #1 to Hard Disk#2, and then reformat Hard Disk#1 to a mac compatible format, and then transfer all the files back. [...]This happens even when I break the files into smaller parts. How can I transfer files from external Hard Drive#1 without receiving the error code above so that I can copy the files to Hard Drive #2 and finally reformat Hard Drive#1?"

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Using NTFS File Format one a Mac:

You can only read from it. You cannot write to it. So, what you need to do is use exFAT format, to make this readable by Mac and Windows.

Use exFAT:

Use an external drive formatted with exFAT would be seen on a PC and on a Mac in System Information… as a connected device, as long as it is mounted on both devices. You just wouldn’t be able to access it, if it is not mounted. As an example, get one of these drives off-the-shelf, and it would be seen: Seagate One Touch SSD. If formatted with APFS, then only the Mac would see it. If formatted with FAT32, only the PC would see it. Note that on the original packaging, As for using a hard drive for Tine Machine Backups, you need to format it with APFS.