External HDD problem

[Andrez]

I tried to open my external HDD but it's like unknown to my system, and it says to format it, otherwise it won't be able to open. I tried some tools like Recuva and some others, but it's just like it does not exist. It used to work fine until now, either in mine and my sister's laptops, but now it does not work neither in mine, nor in hers. I don't want to format it, I have many many many important files (it's 1 TB) so are there ways to keep and save data?