The images you posted appear to be thumbnails, small images created by some program to give a quick and small display of the original. If you took these with a digital camera, there are much larger images stored somewhere on your hard disk and most likely, in the same folder you got these small images from. They probably have a similar name also.
The images straight out of most cameras are typically too large for web posting, actually. You would have to resize them to a size acceptable to the site you are posting to. Most here are posting in the 800 to 1500 pixel size for the wide dimension.
You need a graphics program to make images larger or smaller. But, the files you posted would be very blurry if blown up to a usable size. I use Photoshop for all this, but they others here should be able to direst you to a native Windows program that will change image size respectably.