You still have the older computer and all the other stuff right?
Had you used the "Store Presets with Catalog" option, they would be with the catalog. Not knowing your OS, I'm not sure what path to tell you to find if hopefully, you have the old computer and files. So see:
(.lrtemplate) Presets or templates in the .lrtemplate format are stored at: /Users/[user name]/Library/Application Support/Adobe/Lightroom/[preset or template folder]/[preset or template filename.lrtemplate]
(XMP) Beginning with Lightroom Classic, the existing presets in the.lrtemplate format are automatically converted to a new XMP preset format. After conversion, the new XMP presets are saved at: ~/Library/Application Support/Adobe/CameraRaw/Settings
(Presets stored with the catalog): If you've enabled the Store Presets With This Catalog option in the Lightroom Classic preferences, the presets and templates files are saved at: MacHD/[catalog location]/[catalog folder name]/Lightroom Settings/Settings
Author “Color Management for Photographers" & "Photoshop CC Color Management" (pluralsight.com)