Learn Farsi: اگر بازمانده‌ها اقلام را دریافت کنند، از آنها نیز استفاده خواهند کرد. - If the survivors receive the items, they will also use them.

The formal additive adverb نیز (also / as well) usually comes immediately after the word or phrase it emphasizes. Here it follows از آنها (of them). It often naturally sits right before the verb. If this were less formal, you would typically see هم in this exact same spot.

I see اقلام means items, but doesn't its singular form قلم mean pen?

Yes, قلم means pen, but in formal, administrative, or business contexts it also means an item (like a line item on a list). اقلام is its Arabic broken plural form, making it a very formal way to say items.

Why does the first clause use the subjunctive دریافت کنند while the second uses the future استفاده خواهند کرد?

This is a standard real conditional sentence. In Farsi, the condition after اگر (if) takes the present subjunctive because it is an uncertain event. The result clause then uses the future tense (or sometimes present indicative) to show what will happen if that condition is met.

Why is there an از before آنها in the second clause? Shouldn't it just be a direct object?

The compound verb استفاده کردن (to use) always pairs with the preposition از. In Farsi, you literally say that you make use from something. Because it requires this preposition, you never use the direct object marker را for the thing being used.