Convert icns to txd

Download and install the latest version of Filestar.
Right click on one or more Icns file(s) on your desktop and select Convert with Filestar.
Type convert to txd in the search box.
Press Convert.

What is the difference between .icns and .txd?

Name: macOS Icon Resource File; RenderWare Texture Dictionary
Extension: .icns; .txd
Format: Binary; Binary
Category: Developer; Raster Image
Developer: Apple
Description: It is an icon image file used to show application icons in the macOS Finder and macOS dock. It contains one or several .PNG images and it supports 1bit and 8-bit alpha channels.
MIME Type: image/x-icns; image/x-renderware-txd
Wikipedia: .icns on Wikipedia