Hi Farzad,
You have several options for converting. One of them is the BatchFormatConversion script. Simply specify .jpg as the output extension, select your input image files, an optional output directory, and click OK. In the case of JPEG, you may want to define the following output format hints:
quality nwhere
n is an integer in the range from 0 to 100. The default is 80.
Another possibility, useful if you want to apply some processes in a batch operation before saving the images, is ImageContainer. See
this video from
PixInsight Resources.
To browse image files with previews, statistics and file headers, you can use the File Explorer window. The Blink tool is fantastic to inspect a set of images, including the possibility to get detailed reports on image statistics and FITS header keywords.