Convert\Modify Air fryer from 120v to 220\240
Short answer, no it's not possible to "convert" a 120v appliance to run on 240v, except by replacing the 120v heating element and fans with 240v equivalents.

What is possible however, is to operate the device behind a 240v to 120v mains transformer. Many exist, just find one rated for more Watts than the fryer (1,000W or 1kW). Such a transformer is likely to be heavy and expensive, but as a bonus, other devices will work with it also.