Learn Farsi: همه‌ی رستوران‌ها مورد تفتیش قرار می‌گیرند.

This is a formal passive substitution. moured generally means a case or instance. When linked with the ezâfe to the abstract noun taftish (inspection) and the verb qarâr gereftan (to be placed), it literally translates to 'they are placed as the subject of inspection'. It is used to elevate the register of the sentence, making it sound much more official and bureaucratic.

Why do we use the verbal noun taftish here rather than a Persian verb stem?

The moured-e ... qarâr gereftan structure specifically requires an abstract noun or an action noun to work. You cannot plug in a conjugated verb or a raw past stem. The Arabic-derived verbal noun taftish perfectly fits this role as it acts as a noun representing the action of inspecting.

How would this exact sentence look if we used the standard passive voice instead?

You would use the standard passive auxiliary shodan with the noun, creating the compound verb taftish shodan (to be inspected). The sentence would simply be hame-ye resturân-hâ taftish mi-shavand. The meaning remains exactly the same, but it loses the highly formal tone of the substitution structure.

resturân-hâ (restaurants) are inanimate. Why does the verb mi-girand have a plural ending? I learned inanimate plurals take singular verbs.