NPO operatives numbers

Hey just a question, for small campaigns, how many operatives should you have?

For example I’ve got 10 necrons, 3 scarab swarms and 3 skorpekh destroyers and planning for a nemesis fight at the end. Would this amount of models be enough for say, 3 rounds of fighting?

I’m trying to make a homemade campaign for me and my partner and I wanna make sure I’ve got enough models painted to go through 3 or 4 missions.

Thanks in advance for any help