Hi Elif Karadağ,
Thank you for reaching out here in the Microsoft Community.
In your description, you unplugged the USB after working on the pictures in the USB, and when you plugged it in again, the pictures failed to open with a message that the file type is not supported.
You can plug your USB drive into another computer to see if your pictures open properly on the other computer.
Our initial judgment, it may be that the properties of these photos of yours have been changed, please open Explorer, in the upper toolbar, find the View item, click to open the drop-down box, find the Show item, check the file extension, and then check whether the extension of these photos of yours is .jpg, if not, please change them to .jpg and try to open them again. If not, please make a copy of them and change the extension to .png after you change the name and try again.
If they still won't open even after you make sure they have a .jpg file extension, then you can try opening other images with a .jpg file extension to see if they open properly.
If the other .jpg files also cannot be opened, then please try to open these images using another tool, such as Photo, Snipping Tool or Paint, to see if they can be opened properly using the other opening methods.
Meanwhile, if one of the above mentioned tools can not be opened, please uninstall it and re-download and install it on your computer to see if it can be opened after re-installation.
We kindly remind you here that when you unplug your USB drive or hard disk, please use the Safely Remove Hardware feature in your operating system to avoid files being interrupted while writing and causing damage.
If these photos are important and you wish to recover the contents of the photos, please contact a professional third-party data recovery team, who are highly specialized in this area and will provide you with targeted help.
I hope the above content can help you, if you have any other questions, or the above content did not help you, please continue to contact me, I will provide you with further help, thank you for your support and understanding.
Best regards,
Zev - MSFT | Microsoft Community Support Specialist