المفقودات هنا.

It can be understood both ways.

Grammatically, it is a complete nominal sentence in Arabic: المفقودات = the subject
هنا = the predicate of place

So the full sense is The lost items are here.

At the same time, in real life this kind of wording can also appear on a sign and function like Lost property here.

In Arabic, the present-tense verb to be is usually not stated in sentences like this.

So Arabic says:

المفقودات هنا
literally: the lost items here
natural English: The lost items are here

If you wanted the past, you would add a verb, for example: كانت المفقودات هنا = The lost items were here

المفقودات means lost items, missing things, or lost property, depending on context.

It comes from مفقود, which means lost or missing. Here, though, the word is being used like a noun, not just an adjective. Arabic often does that.

So instead of thinking only lost, think of the lost things or lost property.

The ending -ات is the usual ending of the sound feminine plural in Arabic.

Here it gives the sense of a group of things: مفقودات = lost items

This does not mean the objects are biologically feminine. It is simply a very common Arabic pattern for forming plurals, especially with non-human things and category words.

The basic singular adjective is:

مفقود = lost / missing
مفقودة = lost / missing (feminine)

But in practice, for objects, Arabic often prefers the plural مفقودات as a category word, especially in signs or official contexts.

So while a singular form exists, the plural is often the most natural word when talking about lost property as a general category.

ال is the Arabic definite article, like the in English.

So:

مفقودات = lost items
المفقودات = the lost items

On signs and labels, Arabic very often uses the definite form for categories, so المفقودات sounds natural.

Yes, the l is pronounced here.

That is because the next letter, م, is a moon letter, not a sun letter. So you say:

al-mafqūdāt

The ending -ات is pronounced -āt, and the final t is heard, because it is part of the plural ending.

In careful full pronunciation with case endings, you could say: al-mafqūdātu hunā

In normal pause, you will usually hear: al-mafqūdāt hunā

هنا means here.

Grammatically, it is an adverb of place. In this sentence, it works as the predicate:

المفقودات = the lost items
هنا = here

So the structure is very simple: [subject] + [location]

In fully vowelled MSA, it would be:

المفقوداتُ هنا

The word المفقوداتُ is in the nominative case because it is the subject of a nominal sentence.

هنا does not change its ending here; it stays هنا.

In normal speech or when pausing, the final -u on المفقوداتُ is usually dropped in pronunciation.

Yes, that is possible.

Arabic allows more flexibility in word order than English. Starting with هنا can give a different emphasis, something like Here are the lost items.

But the more neutral and straightforward order is:

المفقودات هنا

So for a learner, that is the safest version to use first.

Usually no. المفقودات normally refers to things, not people.

For missing people, Arabic would normally use different forms such as: المفقودون = the missing people

So this sentence strongly suggests lost property or missing items, not missing persons.