A folder of old bookmarks looks like an easy cleanup job. Then you notice that some of those links are still useful on another computer. Before deleting or merging anything, save a separate copy of the collection you are about to change.
Chrome can make bookmarks saved in your Google Account available across devices. First check the browser profile and account. An export of your personal collection will not protect the work bookmarks in another profile.
Export first, then check the file
In desktop Chrome, open Bookmark Manager from the bookmarks menu. Use the manager’s menu to export bookmarks as HTML. Put the file in a dated folder, with a name that identifies the profile.
Open that file locally and look for a few recognisable folders and links: one recent bookmark, one old reference and one from a nested folder. Check the saved addresses as well as their titles. A file existing on disk is not enough to show that you exported the intended collection.
The HTML contains links, not downloaded copies of all the websites. Keep it private if the addresses or folder names reveal personal information.
Reorganise one folder at a time
Choose a small folder first. Move or remove a few entries, then inspect the result on the devices you actually use. Keep the original export unchanged while doing this.
If you need to import it again, check where the imported entries appear before repeating the operation. Importing a collection is not necessarily an exact undo of every edit. Compare the folders, resolve duplicates carefully and retain the export until the result is clear.