Which version are you referring to? Lightroom Classic or Lightroom? Lightroom mobile refers to Lightroom on a smartphone or tablet (usually).
To transfer your presets to a new computer from Classic you will need to locate and copy them from your old computer first. Go to preferences > presets > show Lightroom presets folder and copy them to an external drive. Connect the drive to your new computer and locate the same folder in your Lightroom Settings folder and paste them in the same location.