How can I integrate customer details from form to square?

If you're only going to capture that information without payment, I'm afraid that's not possible. We only have integration with payments for Square. Here's a guide: How-to-Integrate-Form-with-Square

Note that when a payment is processed through Square, you will be able to see the payer information on your Square dashboard which I believe only includes the payer name, email, and card type.