Once connected, does it create tasks in Monday.com for existing submissions?

We already have existing submission from our form, question.

Once connected, does it create tasks in Monday.com for existing submissions?

You can create new and update existing items using Jotform's Monday.com integration.

Please see my troubleshooting ideas below.

1. Manually create those items on Monday.com from the existing submissions.
2. Create your Jotform form with Monday.com integration and enter existing submissions and submit them to Monday.com. This would add the existing submissions as new items to Monday.com.

We are sorry for any inconvenience this may have caused you. 

Please let us know if you have any questions.

Thank you for your patience!

Related links:

https://www.jotform.com/help/578-how-to-integrate-jotform-with-mondaycom/