"To" is an abbreviation to the verb "estar". "estou" is the presente form of "estar", "Eu estou" but in colloquial way we say "to". What about "com" is the same meaning of "with". Summarize, that sentece is "I am missing you".

Hello! 1) TÔ "Tô" is the colloquial way to say "Estou". "Estou" is the conjugation of the verb "Estar" (To be) for the first person singular. "Eu estou" means "I am" in English. 2) COM "Com" means "with" in English There is no literal translation in English for the sentence "Tô com saudades de você". But this prhase express the following idea: "I miss you" or "I'm missing you".