Help! Unable to access HD without formatting

Hello,

I am using 1TB (Western Digital) external HD for a few months and have a lot of files in it. However, yesterday I could not gain access to the HD as the computer said it need to be formatted. As the files in the HD are very precious to me and may I ask if I still can keep the files after formatting? Or are there other alternatives to recover these files? I browsed a couple of topics in this forum suggesting using data recovery software, but I am not sure which one is best for my situation. Would any kind soul can show me the way? Thank you very much.