How do I know that all of my 1099s have been added to my taxes this year? I though I did them all but itkeeps prompting me to return to the robinhood page to upload more

You can see all forms that have been entered in your TurboTax Online return using the Delete Form option. 

1. After you open your return, go to Tax Tools (left column) >> Tools >> Delete Form.
2. This will bring up a list of all forms. Form 1099's will have a short description to show the source of the information. 
3. Scroll to the bottom and click "Continue With My Return" when you're done.

If you're using TurboTax for Desktop, click the Forms icon in the header. Use Step-by-Step to go back.