Learn Turkish: Beş hemşire hasta, altı polis hazır. - Five nurses are sick, six police officers are ready.

In Turkish, whenever you use a number to specify a quantity, the noun always stays singular. You never add the plural ending (-lar or -ler) after a number. So you literally say "five nurse" (beş hemşire) and "six police officer" (altı polis).

Where is the word for "are" in this sentence?

There isn't a separate word for it! In Turkish, the present tense "to be" (am/is/are) is normally added as a suffix to the end of a word. However, for the third person plural ("they"), this suffix is often left out entirely. The word hasta acts as both "sick" and "are sick" here.

Does polis mean the whole police force or an individual officer?

It can mean both! In English, you have to add "officers" when counting them (six police officers). In Turkish, polis works for the organization, but it is also the standard word for a single police officer.

Why is there just a comma instead of the word ve (and)?

It is very common in Turkish to join two short, related statements with just a comma. You could absolutely put ve (and) in the middle, but leaving it out sounds very natural and conversational.