The simplest way is to apply a filter.
Go to the library module,
Press CTRL + F or CMD + F.
Ensure Text is selected.
Select "any searchable field" in the menu that pops up, ensure "contains all" is selected, then in the field with the magnifying glass type jpg for jpegs, NEF for NEFS and so on.
You can then apply further filter settings if you wish such as colour labels if you wish to filter in the develop module.
Thanks for your help, but if I do that I only get the jpgs that do not have an identical NEF image. I want to be able to separate them.
If by "linked together" you mean that when you import file.nef and file.jpg, you get only one thumbnail in Library Grid view that looks like:
then you have the option Preferences > General > Treat JPEG Files Next To Raw Files As Separate Photos unchecked. To unlink JPEGs and raws, check that option. Then in the Library Folders panel on the left, right click the folder containing the linked files and do Synchronize Folder.
Change one of your metadata filter boxes to "File type" and then click on whichever file type you want displayed.
Thanks for your help.
I did as you said, but all the images were still linked.
Adobe help desk took control of my computer and eventually he synchronized the folder to separate the images.
Many thanks again.