“Sono qui” means “I’m here”. But, you wouldn’t always use that phrase the same way we do in English. If someone asked you something like “ci sei?” (“are you there?”) (in a situation in which you had agreed beforehand on a meeting place) then you might say “sono qui” or “ci sono”. But, in different situations it may be better to say things differently.
For example, if you arrive at someone’s apartment and call up on their buzzer it would be more appropriate to say “sono io” (“it’s me”), provided they were expecting you. If they weren’t expecting you, obviously you would say who you are (“sono…” then your name). Now, in a situation in which you wanted to announce your arrival, like you walk into a room and say “I’m here!”, in that case it would be better to say “eccomi qua”.
It means “I’m here”.
But seriously, with some of these basic language questions containing one or two words, you can just type them in to google translate and you will either get exactly the right answer, or something close enough that you’ll be able to figure it out