I don’t think you can do this directly, but you can do it via GSAK (or other tools that can manipulate a GPX file).
Steps:
1) Open the bookmark list and use the “Create Pocket Query” option. This will build a PQ based on the bookmark list.
2) Run the PQ and download the results
3) Import the results into a new database within GSAK (or equivalent).
4) Use the “Add to Bookmark” option to add these caches to a bookmark list that belongs to you.