If you have a backup of the old places.sqlite file (of the old Firefox profile folder), you can simply replace the new one with the old one or you can do the following. Meant for MacOS/Linux systems, on Windows you'd probably also need to install sqlite.
Close Firefox and copy the new places.sqlite and the old places.sqlite, renamed as old.sqlite, into a folder.
sqlite3 old.sqlite
You need to adjust the-site-to-restore.com to your needs below.
attach "places.sqlite" as new;
insert or ignore into new.moz_places select * from main.moz_places where url like "%the-site-to-restore.com/%";
insert or ignore into new.moz_historyvisits select * from main.moz_historyvisits where place_id in (select id from main.moz_places where url like "%the-site-to-restore.com/%");
places.sqlite now also contains the history visits to the-site-to-restore.com from old.sqlite.