I want to move my custom presets to a new computer.

Here are the locations of the various types of custom preset files:

Virtual instrument preset folder:

%appdata%\Acoustica\Mixcraft\InstPresets

Effect presets folder:

%appdata%\Acoustica\Mixcraft\FX

Effect chain presets:

C:\ProgramData\Acoustica\Mixcraft\MetaPresets7

Samples needed for custom Omni Sampler presets:

C:\ProgramData\Acoustica\Mixcraft\Samples

Here's an example of what the effect chain preset folder looks like in Windows File Explorer: