How do I mention my previous job termination without looking bad?

Mention it briefly and neutrally, focusing on what you learned and why the new role is a better fit for you right now. If they ask directly, be honest but professional: "The company was going through changes" or "we decided it was the right time for both of us" works without getting into negative details. The important thing is to sound positive about the future, not bitter about the past, because that's what's going to matter to whoever's interviewing you.