How can I migrate my ReaditLater bookmarks to the new Pocket system?
In updating from FF55 to 57, I've seemed to have lost my ReadItLater bookmarks. Pocket asks for a login, which I've never had since ReadItLater stored everything offline, altough I've got a username and password saved in my password manager for "chrome://readitlater" and in my Appdata/Roaming profile I've got a readItLater.sqlite, which I assume is my two-thousand-some bookmarks, but I see no way in which I can import this to the new Pocket system, nor do I see a way to migrate.
Send help, I'm lost and afraid.
Make a backup copy of your database for safekeeping (outside of any folder Firefox maintains). Actually, make a copy of your whole Firefox profile folder before doing anything further. See: Back up and restore information in Firefox profiles.
If you download Firefox 55.0.3, disconnect from the internet so Firefox can't update, then run the Fx55 installer, you probably can roll back the program files. Then you could try to figure out whether ReadItLater has any kind of export function that allows you to extract the data to another format that Pocket might be able to import. In particular, if you can export to the standard HTML bookmarks file format, Pocket can import that:
Alternately, you could look for a stand-alone converter.