Required JSON freelancer for Squarespace - Small customisation to confirmation email job

We need a custom change made to a Squarespace confirmation email.

BACKGROUND

When a customer donates money through the Squarespace site, they receive a confirmation email. Squarespace provides some ability to customise this email.

ISSUE

The Squarespace form has a JSON variable { donor.name} which calls on the first and last name that was used during the Credit Card payment in 'STEP 3 PAYMENT'.

FIX NEEDED

We need to call on the first name and last name that is used in 'STEP 4 ADDITIONAL INFORMATION'.

We are not sure if this can be acheived with the right JSON variable, or if some custom code needs to be made/added.

Our Squarespace account is premium so there is an option for code insertion.

Skills & Expertise Required

JSON