HD 3,5' SATAIII 1TB WD 10EARX don't show up after i put it directly on my PC

Hi to all community, I wish to resolve a little-big problem to me, I have the external SATA3 1 TB WD 10EARX working perfectly on usb3 port, but when I try to put it directly on my computer, it doesn’t shows up, I go in the device manager and it see it as a uninitiated Hdd. I wish to use as backup internal, and there are almost 800 gb of data. I don’t want to format. There must be a solution for this, cause I’m using now as external and works! Thank you for help!

Make a backup while the hard drive is connected to the USB 3.0 case and then connect it directly to the PC and format it from there.