STL filetype doesn't appear in import!

Am using free version of Sketchup 2016. Installed 2 free STL importer extensions from Warehouse. STL file format doesn’t appear when trying to import. Other filetypes from the extensions do appear!

Any ideas?

W7 enterprise, running on a very old Dell!
Thank you!

Which ones?
Did you try this one? https://extensions.sketchup.com/en/content/sketchup-stl
Did you make sure they are enabled under Preferences?

Hi thomthom.
How do i get the extension you suggest from my downloads into extensions, please.

The 2 other extensions are in preferences.
Thank you!

Open the preferences->extensions panel, click install extension, and select the downloaded .rbz in the explorer panel that opens.