Robinhood is a financial services company.  You do Not file state tax return for the state where Robinhood is based.

You report investment sales on a federal tax return.  Any investment sales or losses are included in your resident state gross income on the resident state tax return.

---

@ndnguyen wrote:

One more question which might be trivial. Do I have to file state's taxes for the states where companies I bought stocks from are located? Some companies' stocks I bought are from California. 

---

No.  You only have to file a nonresident state income tax return if you physically worked in another state other than your resident state.

Just because you own shares of a company that is based outside of your resident state in no way means that you have to file a state tax return for the state where the company is located.