Hello!
I completely get where you're coming from - a lot of people don't have a single "lightbulb moment" that pushed them toward law, and that's honestly very normal! However, I'd say it's best to focus your answer around one specific personal experience, even if your motivation developed gradually. The question specifically asks for "a specific personal experience", so I would say they're looking for you to anchor your answer around a moment or situation that you can describe clearly.
That doesn't mean you need a big "lightbulb moment" - it could just be one experience that represents or crystallised what motivated you to pursue a career in law. For example, something that made you appreciate problem-solving, negotiation, advocacy, or international collaboration - this can be any experience that ties into your wider motivations towards law.
I think it's a great idea to bring in your travels or other broader experiences, I would just try and pick one defining example. For instance, you might choose a moment that stood out in particular - such as an interaction, observation, or situation that sparked your curiosity about how law shapes society, business, or people's lives. You can then explain how that particular experience made you start thinking about law in a more concrete way and influenced what kind of work or environment you see yourself in.
In other words, I would use one experience as the lens through which you show how your motivation developed. That way, your answer stays focused and personal while still reflecting the wider journey that's led you towards a legal career.
I hope that helps, and best of luck with the application!