How do I search for all the cards where a specific field contains a capital letter?
For example, I have cards with three fields. Question, Answer, and Extra. I want to search the question field for all the cards which contain a capital letter in that field.
That version is almost 4 years old. According to the manual (see link) you can’t use regex, and without regex, you might be out of luck (“Standard searches are case insensitive for Latin characters - a-z will match A-Z, and vice versa.”).
If this is important to you, you should consider updating to a more recent version. Making that big a jump, be sure to read the upgrade notes (Platform Notes - Anki Manual), and be mindful of any add-ons that you need your version to be compatible with.