I came here long ago. Is the correct statement. The other mixes the tenses. Came - past tense come - present tense come here long ago - mixed past tense and present tense

I have come here long ago. Wrong. I came here long ago. Right. You can't use the present perfect with that time indicator. By the way 'long ago' sounds more literary, it's unlikely someone would say it in speech. 'A long time ago' is more common in daily speech.