Cognito Forms Sums Help

I need help. I've exhausted ChatGPT in looking for formulas, and Cognito is unclear on more advanced formulas. Nothing in the examples pertains to my particular situation. I must grab a value from a drop-down Choices Field on form 1.They select how many people they register for a class, with a monetary value attached. I need that value to go into a radio button Choices field on Form 3, where they can select a payment method (Credit Card, transfer, Cheque) for the amount they chose on Form 1 and have it collect the payment.