Learn Russian: Директор хочет убедиться, действительный ли этот сертификат. - The director wants to confirm whether this certificate is valid.

The particle ли means "whether" or "if" in indirect yes/no questions. The rule is that ли must immediately follow the exact word that is being questioned. Since the director's main question is about whether the certificate is valid, the adjective действительный goes first, followed directly by ли.

Can I use если instead of ли in this sentence since the English translation could say "confirm if"?

No, this is a very common trap! In English, we often use "if" interchangeably with "whether". However, Russian strictly uses если only for conditions ("if X happens, then Y"). For indirect questions asking "whether or not" something is true, you must always use ли.

What dictates the word order in the second half of the sentence (действительный ли этот сертификат)?

In a ли clause, the word in question is pulled to the very front of that specific clause. Then ли attaches to it as the second word, and the subject and remaining words follow. Because we are questioning the adjective, the order has to be действительный + ли + the subject (этот сертификат).

The English translation says "confirm", but isn't убедиться related to the word for "convince"?