Each camera model comes with its own unique raw format. Any older conversion sofware won't be able to read the raw files from the new camera. Only current versions of Elements can be updated to recognize new formats.
For older versions, Adobe provides the free DNGconverter mentioned in the above faq. That standalone software (not a plugin) can batch convert a whole folder of your raw files to the DNG raw format that your PSE version can read and edit. An additional batch step, but free with the same quality.
. . . in addition to the DNG converter solution there is a workaround. See my post here. I have not tried ACR 13 with Elements 2018 but it should work. Note that in Step 9 of the Adobe workaround, the version number for Elements 2018 is Elements 16. So the path you should be looking for is: C:\Program Files\Common Files\Adobe\Plug-Ins\Elements 16\File Formats.