Unfortunately, that can't be accomplished by an extension. If there are quite a few extensions to update, probably the easiest method is to temporarily select 'Update Add-ons Automatically', then select 'Check for Updates', and then afterwards deselect 'Update Add-ons Automatically'. This, of course, is somewhat tedious.

There is a Bugzilla issue requesting an 'Install Updates' button that would be helpful in this situation, however it is over 5 years old ( https://bugzilla.mozilla.org/show_bug.cgi?id=1560834 ).