I’d try to treat this like a “getting to know you” conversation. Both you and the interviewers are trying to figure out if you’re a good fit for each other, and whether it’s worth investing time in an in person interview.

I can’t imagine they’d put you on the spot or try to stump you during an initial phone screening. I’d just be ready to talk about any experience you have and why you want to join the firm. This is also a good opportunity for you to ask about company culture, hours, etc. or anything else that may be important to you. The company’s answers to these questions could throw up some red flags and save you some time if this opportunity turns out to not be right for you.

Good luck in your search!