My parents were going to name me zaakirah but then an imam told them the correct name is actually Thaakirah and not Zaakirah. Is this true? Zaakirah seems to be more popular though

The original, standard pronunciation is Thaakirah, with the "th" as in the English word "that". But since "th" is hard to pronounce, both Arabs and non-Arabs pronounce it as Zaakirah, and in fact that vast majority of Arabs would be surprised if you pronounced your name Thaakirah, since it sounds unnatural to them, it sounds too formal and old.

Thus when writing your name in English, or when saying your name, use Zaakirah. But if you write your name in Arabic, you'd have to write it as ذَاكِرَة, which is pronounced Thaakirah in standard Arabic and Zaakirah in spoken (non-formal) Arabic.

Therefore the only issue is how you write your name in Arabic. As for how you write it in other languages, and how you say your name, then Zaakirah is perfectly fine.

As an example, Arabs say Usman, even though the standard name is written as Uthman, because spoken Arabic is very different from written Arabic