Hello, according to your description, considering you are the first user of Mac, here you should know that:
There is a file system called NTFS, developed by Microsoft, which can only be read on Mac. Therefore, you're suggested to utilize an NTFS driver for Mac if you want to write(like you're saying “save”).
iBoysoft NTFS for Mac is a good choice for you, helping you read and write seamlessly on Mac. And with this tool, you needn't reformat the drive, which must erase all your data.
Hope you can use it normally at last.
Also read: You Can Only Read Internal/External Hard Drive on Mac
