MacBook Air mid 2013
Does Apple still support Catalina?
MacBook Air 13″, macOS 10.15
FYI, your laptop can run macOS 11.x Big Sur.
macOS Big Sur - Technical Specifications
You can find links to various macOS installers within this Apple article which also includes optional instructions for creating bootable macOS USB installers:
How to create a bootable installer for macOS - Apple Support
