Learn Farsi: در این روتین آرایش، به جز کرم، از این سرم استفاده می‌شود. - In this makeup routine, except for the cream, this serum is used.

This is an impersonal passive of a prepositional verb, which is the focus of this lesson. In the active voice, the verb "to use" is از چیزی استفاده کردن (literally: to do usage from something). When converting this to the passive voice (استفاده می‌شود), Farsi strictly keeps the preposition از. So instead of making "this serum" the direct grammatical subject, Farsi structures it as "from this serum, usage is done."

Can I just drop the از and say این سرم استفاده می‌شود?

You shouldn't. While English directly says "the serum is used," dropping از sounds unnatural to Farsi speakers. Because the noun استفاده inherently requires از to link to the object being utilized, you must keep the preposition even when the sentence is passive.

The words کرم and سرم look like English words. How are they pronounced?

They are loanwords from French, which Farsi frequently uses for cosmetic and medical terms. "Cream" is کرم and is pronounced kerem — be careful not to pronounce it kerm, which means "worm"! "Serum" is سرم and is pronounced serom.

What is the phrase for "except for" here, and what are some B2-level alternatives?

The phrase used here is به جز (be joz), which is very common and can also be written as one word (بجز). Other excellent alternatives you should know at this level are (gheyr az) and (savay-e). All of them work perfectly to mean "excluding" an item in a list like this.