I would suggest to first of all use the scale bar information to scale the images so that they all have the same scale ((Image->Scale…).
You could then try to use one of the stitching plugins to combine the image. I had a quick go using pairwise stitching in Fiji-ImageJ (Plugins -> Stitching -> Pairwise stitching). The result wasn’t that great, but you might be able to improve on it working from the original images.
There is also another plugin MosaicJ (http://bigwww.epfl.ch/thevenaz/mosaicj/), which I have used for similar tasks in the past. It allows you to manually pre-arrange your images and does various transformations of the images if necessary/selected.
Finally, if everything else fails, you could do it completely manually by increasing the canvas size of one of the images and then copy and paste the other images in the appropriate place. If necessary, you can first rotate the images so that they match each other. A quick attempt using your provided image resulted in the image below.
Hope this helps,