I want my form to calculate an estimate price

https://form.jotform.com/202876365558064

I want my form to take the mileage from the first screen and multiply it by a value to provide an estimate of the price.

You would need to add a FORM CALCULATION widget to the form to calculate the cost based on the KM value:

Then just pass the result to the payment field. Here's a guide on how-to-pass-a-calculation-to-a-payment-field.

Another approach would be to use conditions to manually insert a value to the calculation based on the criteria you set. So for example, 1KM-33KM would be priced at 400ZAR , right? Then use this condition:

Do this for all the other criteria you have.

You can then pass the value of the CALCULATE field to the payment field using the method I provided above.