Are you looking to to a new computer, or are you trying to reset your campaign data specifically?
If the game crashes on load and your save file is missing, it may have been corrupted. Check Windows Recycle Bin. If you find savegame.svg there, restore it, then manually copy it back to the players folder.
If you are moving save files to a new PC, ensure you disable synchronization temporarily for the game. If active, Steam may overwrite your manually placed files with older versions from the cloud.
If Steam Cloud is enabled, copies of these files are also stored in your local Steam userdata folder: C:\Program Files (x86)\Steam\userdata\ \292730\remote\ . Microsoft Store / Xbox Game Pass