NTFS is a newer file system for your hard drive, more secure and recognises larger drives than FAT32, by way of compression. Or something like that.
The only way to convert is by formatting the drive thus wiping it clean of data and starting anew.
I converted my desktop last year from FAT to NTFS and I certainly did not have to format the drive. It is very simple to do, takes a minute and does not affect your files, software of anything.